Prognosis

Prognosis (Gk pro before, gnosis knowledge) is foreseeing the onset, the character of development, and the outcome of a disease. Prognosis is based on the knowledge of regularities of the course of pathological pro­cesses. Prognosis is also defined as diagnosis of the future.

The power of forecasting was highly esteemed in ancient Greece. Hip­pocrates would repeatedly stress that foreseeing would be the best what a physician might do, and that the physician might be of better use to those patients who could control the development of the disease in themselves provided the physician could forecast a possible disease as much before the actual onset of the disease as possible. Prognosis is necessary for successful treatment, but a correct prognosis also improves the patient's confidence in the physician. In Hippocrates' opinion timely prognosis of incurable cases saves medical art from accusation.

General problems of prognosis are the necessary and also difficult aspects of clinical medicine. Nevertheless prognosis has been given much less attention than diagnosis until recent times. The importance of pro­gnosis in the clinic depends on the main purposes of practical medicine, namely prevention of diseases and treatment of patients. In this respect the work of a physician is like that of an investigator: " studying laws in order to be able to predict phenomena, and to predict phenomena in order to be able to master them" (Loeb). Knowledge of the aetiology of diseases, and of harmful working and living conditions which might impair health enables the physician to foretell under which conditions a given person or a group of people are likely to develop a particular disease. This is a prere­quisite condition for successful personal and social hygiene.

Extensive prophylactic measures against epidemic diseases are based on the faculty to foresee possible ways of spreading of the contagious disease. For example, if a case of diphtheria or typhus is revealed, hygienic-prophylactic measures are undertaken on a broad scale, while the threat of an outbreak of seasonal influenza should involve mass-scale vaccination of the population, etc. In cases where a complication or a relapse is possi­ble, prophylactic therapy is prescribed to prevent, for example, relapses of rheumatic fever, peptic ulcer, etc. Work of the public health services is based on the prognosis of changes in the incidence and localization of general illness among the population and of individual diseases in par­ticular.

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Analysis of medical work, like that of any other practical activity, shows that it is always connected with the prognosis of a given disease and with the forecasting of the results of medical and prophylactic measures. In his work, the physician must envisage the results (respice finem). The pro­gnostic evaluation determines the selection of therapeutic means; for exam­ple, the discovery of even a small cancer tumour dictates a radical opera­tion. Prescription of any medicinal preparation should be supported by a consideration of possible various side-effects and consequences of this therapy. For example, when giving a purgative, the physician must con­sider a possible negative effect of this measure, as in acute appendicitis. Development of a disease in accordance with the prognosis can indirectly confirm the correctness of the diagnosis. Prognosis is thus an indispensable part of practical medicine.

Forms of prognosis. The most important problem that concerns both the patient and the physician is whether the illness is fatal (prognosis quoad vitam). The other problem is the question of complete recovery (prognosis quoad valitudinem), how long the patient can live (prognosis quoad longitudinem vitae), what will be the progress of the disease in the im­mediate and far-off future (prognosis quoad decursum morbi), and whether the patient's functions will be restored (prognosis quoad func-tionem).

The physician must foresee the results of his therapy, the dangers of operative intervention and decide whether the patient will recover com­pletely with time or whether he will be unable to continue with his normal life and occupation. If not, then he must decide what form of labour will be safe for the patient in his new condition (prognosis quoad laborem). Prognosis can be favourable, doubtful, bad, or unfavourable (prognosis bona, dubia, mala, pessima). Prognosis can also be lethal (prognosis lethalis).

Prognosis of a disease. Prognosis of a disease depends in the first in­stance on accurate and complete diagnosis. " When foretelling, the physi­cian takes into consideration the main disease, the condition of the patient, his sex, age, social position, hereditary traits, the changes that have oc­curred in his condition as the result of previous diseases, his adaptability and the psychic and physical conditions under which the patient has been living. The physician cannot know the degree of stability of the patient's vital organs" (Botkin). The physician first considers the danger of a given disease (mortality rate, incidence of complete recovery, and residual effects following recovery). Prognosis is based mainly on statistical data concern­ing the disease.

The general prognosis of a disease is determined by the following two factors, namely the essence of the disease and advances made in modern therapy. Prognostic study of diseases has revealed with sufficient accuracy

that there exist (a) diseases that are completely incurable, e.g. leucoses; (b) diseases that are essentially very dangerous but which are curable at their early stages (e.g. sepsis, malignant tumours) and undoubtedly lethal in their late stages (e.g. profuse metastases of cancer or sarcoma). The other group includes diseases that resolve either spontaneously, or with the ap­propriate treatment (acute rhinitis, acute alimentary gastritis, minor in­juries); these diseases result in complete recovery (restitutio ad integrum), although any disease causes changes in the body (residual effects due to the disease itself or its treatment, e.g. operative).

However, most diseases occupy an intermediate position between these two extremes (from the point of view of their prognostic assessment). These diseases vary greatly in terms of the degree of danger that they con­stitute to life. Many incurable diseases present no immediate danger to the patient's life and may last for years, only imparing the working capacity of the sufferer. Mortality in various diseases varies with time depending on advances in medicine and practical health care; the general prognosis of diseases improves with time as well. For example, many infectious diseases can now be successfully treated following the discovery of antibiotics; the use of vitamin B₁₂ has moved Biermer disease (pernicious anaemia) to the category of curable diseases; certain congenital heart defects can now be corrected due to advances in heart surgery, etc.

The gravity of a disease is determined by certain signs, such as localiza­tion and extent of affliction, the body's reaction, the degree of functional disorder of the vital organs and the reversibility of functional and mor­phological changes of the body. Functional diagnosis gives valuable infor­mation for the prognosis of diseases.

Prognosis of the course of a disease foretells the length and possible complications of the disease. All diseases are classified as chronic and acute by their duration. Acute infectious diseases usually continue for a definite time depending on the nature of the pathology and immunobiological reac­tion of the patient's organism. Knowledge of the length of the disease is im­portant for orientation in a particular case, sometimes for checking cor­rectness of the diagnosis, or for the search of a developing complication (e.g. post-influenzal pneumonia). Statistical data on the incidence of com­plications in a given disease are no less important (e.g. small intestine per­foration in typhoid fever, gastro-intestinal haemorrhage in cirrhosis of the liver, post-operative thrombosis of the veins). If the physician is aware of complications that may arise in a given disease, they can be timely revealed and better precluded. By foreseeing possible complications, the physician can take timely measures to prevent their development, e.g. by giving an­ticoagulants to prevent thrombosis, CO₂ respiration to prevent post­operative atelectasis of the lungs, etc.

The course of the disease and its complications depend on the

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pathogenesis of the disease and individual properties of the patient's organism. Prognosis is always more favourable in the young: youth is the best friend of the patient. The course of the disease is influenced by con­stitution, hereditary factors, past diseases, living conditions, and also the health of the patient before the onset of the disease. Social conditions are often decisive for the prognosis of the disease, especially in capitalist coun­tries, where medical aid is sometimes very expensive.

Evaluation of each symptom is very important for prognosis. The main diagnosis of the disease, knowledge of the aetiology and essence of the pathology give a clue to the physician in his forecast concerning possible curability or incurability and the duration of the disease. Symptoms of the disease give a concrete picture of its gravity and the degree of danger for life, and can be used to foresee the nearest course of the disease in a given patient, i.e. to establish an individual prognosis. The appearance of the eyes, voice, or strength of a handshake are informative of the patient's condition. The posture of the patient in his bed (active, passive, forced) is also prognostically important. Inspection of the tongue is necessary: a dry tongue is almost always an alarming sign; the loss of appetite is regarded as the " despair of nature in overcoming the disease", while good appetite is a " flag of health" (Obraztsov). The prognostic assessment of any symptom depends on the knowledge of its pathogenesis and the role in the main pro­cess. Dyspnoea, for example, in mitral stenosis and left ventricular failure due to hypertension has different prognostic significance. Diagnostic and prognostic importance of this or that symptom often coincide. For exam­ple, pulsus alternans or the gallop rhythm indicate a serious heart insuffi­ciency. Observation of changes in separate symptoms has different pro­gnostic importance. For example, growing tachycardia or change in the arterial pressure can be used as a guide to understanding the direction in which the disease develops. It should be remembered that a symptom (e.g. leucocytosis or fever) cannot always be indicative of disease gravity. It can only be a manifestation of the protective response of the body. The absence or weakening of such a reaction (i.e. the absence of pronounced symptoms) sometimes indicates gravity of prognosis, e.g. leucopenia in appendicitis or insignificant rise in temperature in a cachectic patient with pneumonia.

Individual reactivity of the patient's body requires a thorough clinical analysis. For example, neurotic patients can severely suffer from a mild disease, while some patients with grave diseases may abstain from any complaints. Each separate symptom can acquire a prognostic importance only when it can be used to judge on the function of the organ and the general condition of the body. A symptom becomes prognostically impor­tant only when it is considered in connection with the essence of the disease. For example, a sudden death can occur during the first pain attack in coronary failure.

Hereditary factors are important because the patient may be predis­posed to some diseases, e.g. hypertension, obesity, etc. Knowledge of fami­ly diseases and the cause of death of parents is sometimes of great impor­tance in assessing the probable development and the course of this or that disease in a particular patient. Age of parents is, for example, important for prognosis of a disease in offspring.

The appearance of a patient, the make-up of the body, and the con­stitution are prognostically important. It should be remembered however that subtility by no means excludes longevity even of a sickly looking per­son. Quite the contrary, a blooming person may more readily become a vic­tim of an acute infection or cerebral apoplexy than an asthenic person. Ex­cess weight, and especially predisposition to obesity, are aggravating fac­tors.

Past diseases often change the body substantially. Stable immunity develops after acute infections attended by skin eruptions (measles, scarlet fever, smallpox, etc.). Other diseases, e.g. acute lobar pneumonia, rheumatic fever or peptic ulcer often recur.

Study of a healthy person for prognostic purpose should be as complete as the study of patients because prophylaxis of diseases is the main princi­ple of the Soviet public health system. In this connection the dispensary system is being constantly broadened in this country. Dispensary observa­tion of practically healthy population help reveal by X-ray studies cancer of the lung in persons who never complained of any malaise, or diagnose chronic nephritis or diabetes mellitus by the urinalysis. More common, however, is the discovery in practically healthy people of a tendency to develop certain chronic diseases or pre-clinical stage of diseases, e.g. hyper-cholesterolaemia which is a sign of disturbed lipid metabolism that often precedes the development of atherosclerosis, or moderate alimentary hyperglycaemia which is a sign of a prediabetic disorder in carbohydrate metabolism. No less important is the tendency to elevation of arterial pressure during emotional stress since it may indicate (not obligatory) the development of essential hypertension in future. Revealing signs of allergic reaction of the body (e.g. nettle rash) enables the physician to predict possi­ble similar reactions and partially foresee the course of other diseases and the response to their treatment.

Determination of the type of higher nervous activity is very important for assessing the character of emotional reactions, which can (under special conditions) give rise to the development of neuroses or diseases of the cen­tral nervous system, vessels, etc. Furthermore, it should be remembered that certain people can be neglectful with respect to the prevention or treat­ment of a disease, as distinct from other people who, on the contrary, may be overanxious about their health or disease (which can sometimes be only imaginary).

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Occupation or working conditions can sometimes be decisive for the health of a person, especially so if the character of work does not corres­pond to constitution of the person. The positive role of work in preserva­tion of health of man is revealed, for example, in certain cases of depres-or low somatic tone, or decreased resistance to some diseases in

sion

middle-aged healthy persons who retire to pension. Inadequate living con­ditions (housing, nutrition, climate, etc.) and unhygienic habits predispose to the development of various diseases. Overeating, smoking, alcohol, etc., should be regarded as pathogenic factors which often cause grave diseases the near or remote future. Foreseeing the conditions under which

in

diseases can develop is requisite for their prevention.

General prognosis is closely connected with advances in therapy; mor­tality from most diseases drops from year to year thanks to new discoveries in medicine and improved organization of the public health system. Mor­tality in pneumonia was as high as 25-40 per cent before chemotherapeutic preparations came into use. After the discovery of antibiotics this figure dropped to 8—10 per cent and even lower. The specific causative agent is very important for the prognosis in pneumonia. Prognosis is worse with type III pneumococcus than with types I and II. The percentage of fatal outcomes in epidemics of one and the same disease differs. This was earlier designated by the term " genius epidemicus". This depends on changeabili­ty in the pathogenic properties of the causative agent and resistance of the body. The latter factor was decisive for the character of pandemic influen­za after World War I. Prophylactic vaccinations are also important for a milder course of infections.

Depending on aetiology and pathogenesis of each infectious or other disease, a specific organ is mostly affected, e.g. myocardium is affected in diphtheria, vessels in louse-borne fever. Maximum attention should therefore be paid to observation of the function of the corresponding systems or organs so that the degree of their affection might be assessed and possible outcome predicted. In all cases, the physician must observe and study vitally important organs and systems (blood circulation, respira­tion, etc.). This observation is very important for the prognosis of the near and.remote outcome of the disease. All possible complications (e.g. pneumonia in influenza, intestinal haemorrhage in louse-borne fever, etc.) should be considered by the physician in order to prognose the course of the disease and to control timely a sudden worsening of the patient's condi­tion. No less important is it to know during what period of the disease this or that complication may develop. Any impairment of the patient's condi­tion will not then be unexpected. Daily observation of patients with grave infectious diseases helps determine the tendency or direction of the pathological process. The physician should take pulse and temperature, determine leucocytosis, the character of urination, etc.

It is more difficult to foresee the outcome of a chronic than of an acute disease. Prognosis of some incurable diseases almost entirely depends on the therapy with preparations that compensate for the pathological changes (e.g. diabetes mellitus, myxoedema, etc.). The course of many chronic diseases associated with incurable defects in the structure and func­tion of some organs can only be assessed after observation of the patient and assessment of the progress of the pathology (e.g. in lung emphysema, atherosclerosis, heart valve defects, etc.). The compensation of the affec­tion or defect is very important for the prognosis of the disease. An exam­ple of almost unlimited compensation ability of the body is good subjective condition and working capacity of patients with fully closed coronary artery provided there is sufficient time for a vascular collateral to develop. When one of paired organs is lost (e.g. one kidney) the remaining organ en­sures normal function for an indefinitely long time. It is known that preser­vation of a small portion of any organ, e.g. of the liver, the lung, etc., is compatible with life, which may sometimes be quite active. Consideration of adaptability of the body to the changed environmental conditions is the main basis for a prognosis in chronic diseases. Adaptability, which is the main property of any living organism, differs, however, in various sub­jects. Adaptability of healthy people to hard environmental conditions depends not only on the congenital factors but also on training in direct sense of this word (e.g. in physical strain) and also in a figurative sense; for example, people who had successful operations in their past history, better tolerate a new one. " Hot-house" conditions impair resistance of the body. A disease itself is one of the forms of more or less adequate adaptation of the body. For example, a local inflammation prevents generalization of in­fection and often removes the causative agent or unjury leading to com­plete recovery. At the same time, a chronic disease or an injury has its ef­fect on the future life of man.

Individual traits of the patient's temperament are important to predict the outcome of a disease and working capacity of the patient after his recovery. Some patients become disabled by insignificant affections, while others bravely challenge grave diseases, such as chronic arthritis or heart diseases, and continue living an active life. Some patients are passive in their attitude to the prescribed therapy while others actively fight the disease and recover their working capacity.

Almost any chronic disease is characterized by certain periodicity, in which relapses alternate with remissions. Remissions and relapses depend on both special features of pathology and on the environmental conditions, which sometimes are difficult to control. Concomitance of several pathological processes markedly aggravates the prognosis. According to certain authors, signs of coronary atherosclerosis were observed in 10 out °f 1000 practically healthy aged male patients during four years. In cases

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with concurrent hypercholesterolaemia, obesity, and hypertension (or any two of these three diseases), the incidence of coronary affections was as high as 143 per 1000 patients (i.e. more than ten times higher). Develop­ment of an acute disease in a patient with a chronic one (e.g. infection in a diabetes patient) is especially dangerous.

Prognostic errors. The difficulty of prognosis is that it is based on the diagnosis. " Diagnosis is only a more or less probable hypothesis. Foresee­ing based on this hypothesis is, of course, less probable than the first main hypothesis, the more so that many unknown factors continue their effect on the patient during the time when this medical problem is being solved" (Botkin). Difficulties in foreseeing the course of a disease are emphasized by all clinicians. " Despite advances in modern medicine, the most difficult problem is to foresee the course of the disease and its outcome" (Kon-chalovsky). Incorrect or incomplete diagnosis is the main source of the er­roneous prognosis, because a correct prognosis is only possible with a cor­rect diagnosis.

A physician's forecast consists in determining the conditions under which this or that phenomenon is likely to occur, and prognostic error depends on the incomplete knowledge of these conditions. Diagnosis is in­complete if only the disease is diagnosed while the condition of the patient has not been studied. It is difficult then to predict the course of the disease in the nearest or remote future.

Prognostic errors often arise from the inaccurate determination of the compensatory properties and reserve forces of the organism. Psychological and subjective features of a physician may become the source of prognostic errors. For example, in his desire to see the patient recovered from the disease, the physician may misinterpret new and sometimes dangerous symptoms, which might be taken as some extraneous factors rather than the signs of the main disease. Prognosis of the remote future is still more difficult than the foreseeing of the immediate events because new condi­tions may occur which would affect the main course of the disease.

Prognosis and the patient. The patient is usually mostly interested in prognosis rather than diagnosis, which is his second interest. But the diagnosis has a prognostic importance to the patient as well, since it may tell him whether or not his disease is curable. The physician should always be ready to answer this question about the diagnosis. The relations between the physician and the patient should obey the main purpose of medicine, namely, prevention and treatment of disease. The prognosis that the physi­cian gives to his patient should not therefore contradict this main medical law. The prognosis of cancer should always be excluded from conversation with the patient and even with his relatives if there is the danger that the pa­tient might know the truth from them. Botkin wrote, " I think that the

physician has no right to tell his patient his doubts concerning possible un­favourable outcome of his disease". Possible diagnostic errors should also be taken into consideration. That physician is the best who can persuade the patient that the disease is curable. Sometimes this persuasion is the best medicine.

Any disease evokes the feeling of fear, anxiety, and other unfavourable emotions, and the prognosis should not therefore aggravate the condition of the patient. The responsibility of the physician for the prognosis is thus very high. The physician takes also high responsibility when he recom­mends that the patient should change his occupation or place of residence, or else the mode of life for a long time. The physician should abstain from careless words or gestures that might reveal the gravity of the prognosis. The physician should put his prognosis in words that might be clearly understood by the patient without undue details. Uncertain prognosis may aggravate the patient's anxiety by arousing doubts in him; neither should the physician outline definite terms for a complete recovery. The predicted term may prove incorrect and this may strengthen the patient's anxiety and decrease his confidence in the physician. The prognostic evaluation should be worded in conventional terms such as, for example, " You will recover if you follow my prescriptions", and the like. In some cases it is reasonable to give the patient a wrong diagnosis, e.g. of tuberculosis, if the patient has cancer. This will encourage the patient. The foretelling should be worded neither too seriously nor too carelessly. In all cases it should be close to the real one but supplemented with optimism in severe cases.

A favourable prognosis should be spoken out without waiting for the patient's question, because some patients choose not to know the truth from the fear of losing any hope. It is not infrequent that some patients (physicians included) choose to deceive themselves despite the vivid signs of incurability of their disease (e.g. cancer). This should be regarded as a peculiar protective reaction. If there is no other way to persuade a patient to give consent to an operation in cancer of the stomach, for example, it is reasonable to tell him half-truth by saying that the operation is necessary to remove a tumour which may otherwise become malignant. In other words, the prognosis depends on the necessity of treatment. The prognosis should therefore be not only definite and encouraging, but it will also show possi­ble danger if the patient does not follow medical recommendations. This will strengthen the patient's confidence in the physician. The physician has to conceal grave truth from his patient but his condition should be assessed Properly and the relatives should be informed of this condition, provided the physician is sure that the relatives will keep the truth from the patient.

Possible diagnostic error should always be considered. But prognosis depends on diagnosis, and in^v dubious cases it is better to abstain from the

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forecast rather than to show undue optimism. The patient and his relatives should be prepared for a possible worsening in the patient's condition. Such a prediction prevents possible depression which can develop from a sudden and unexpected exacerbation of symptoms. It is necessary to in­form the patient of the approximate duration of the disease and treatment, in order to prepare him for a possible protracted course of treatment and slow recovery.

Prognostic methods. Methods of medical prognostication have changed with the development of medicine. Prognosis at the early stage of medical science was only empirical; it is still important now. It consists in comparison of the general condition and functions of the patient's organs with those of a healthy person, the degree of deviation being the measure of the condition gravity. Comparison of the vital functions and the anatomical changes in the patient with those of a healthy person is the first step in the diagnostic and prognostic study. But the conclusion will be only very general. Marked deviation of the bodily functions from normal in­dicate danger but cannot be used for a definite prognosis of the outcome of the disease because functional disorders often depend not only on the af­fection but are often a protective and useful response of the body, e.g. vomiting in poisoning, cough in the presence of foreign bodies in the respiratory ducts, etc. During repeated examinations in the modern clinic, the present condition of the patient and the individual symptoms are com­pared with those observed during earlier examinations. This comparison is very important for judgement on the direction of the pathological process, and for assessment of worsening or improvement of the patient's condi­tion.

Another empirical method is based on a suggestion of possible occur­rence or a relapse of an event provided a phenomenon preceding this event was noted. This kind of prognostic signs can be regarded as a necessity only if the events follow one another as cause and effect. But two events that follow one another may have no causal dependence, or they may be effects of one and the same cause. Hence only relative value of such signs.

Still another prognostic method is based on conclusions derived from many separate events, e.g. on statistical regularity. Statistical data on the outcomes of diseases are of general importance and hold for mass-scale phenomena, but they can give only tentative information for the prognosis in individual cases (higher or lower probability of the expected event). Speculations are based on diagnosis, but the patient's condition may vary with one and the same diagnosis (e.g. tuberculosis, myocardial infarction, etc.) depending on many conditions.

Personal experience is an important factor in prognosis. It is equally important for correct prognosis and correct diagnosis. Experience of a

physician depends on his memory, i.e. the power to recollect information on more or less significant number of similar cases. In contrast to scientific investigation, medical experience of a physician cannot be substantiated statistically while generalizations based on personal experience are not suf­ficiently accurate. Lengthy observation of patients from the onset of the disease to its end is valuable for aquisition of experience in foretelling. Therefore formerly prognostic conclusions of a family doctor were often more correct than conclusions of scientific consultants. Once the physician knows individual properties of a given patient, it is easier for him to predict the response of his patient to this or that aetiological factor.

Scientific knowledge of the course and outcome of a disease is as im­portant as a personal experience of a physician. These data are used to predict the patient's condition in future. Personal experience of a physician is always based on achievements in medicine. Scientific investigations give information on the possible course of a disease depending on its form, stage, the patient's constitution, and the like, and also explain the causes of such a course, the mechanisms of body affection, the character and signs of convalescence, i.e. they establish regularities of patho- and sanogenesis of a disease. Scientific prediction is based on the knowledge of regularities of a given pathological process, e.g. malignant newgrowth, inflammation, acute infection, etc. Once effects of particular causes are known, one can foretell future developments.

Modern medical prognosis requires a thorough clinical analysis and evaluation of the symptoms of a disease, consideration of the progress of pathology and protective processes or sanogenesis, and also vital reserves of the important body organs. A single examination can be used to assess the gravity of the present condition of the patient, while the direction of the pathology can be determined from anamnesis and from lengthy observa­tion of the patient. But various signs of a disease, e.g. temperature, pulse, respiration, leucocytosis, can vary sharply with the course of the process. The curve of a high temperature in acute lobar pneumonia always drops at the end which can be either due to the high antibody level (crisis) and begin­ning convalescence, or due to a grave toxicosis and a circulatory collapse. Observation also gives information on the effects of the therapy. The number of factors involved in prognostication of the disease is thus greater than for its diagnosis. They are supplemented by the results of the prescrib­ed treatment, and speculations of a physician in prognosis are more com­plicated than during statement of the patient's condition. Prognosis is bas­ed on regularities of the pathological processes and knowledge of the ac­tion of aetiological factors.

The logical fundamentals of prognosis are more complicated and differ substantially from diagnostic knowledge. In order to diagnose the present

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condition of a person, the physician examines him, finds and evaluates the symptoms. By examining the combination and sequence of the symptoms, the physician concludes on the character of the pathology (i.e. he proceeds from phenomena to the essence). Finally, he investigates the aetiology and conditions under which the disease developed. The physician can reconstruct the picture of the development of the disease (i.e. the past history) from the present conditions and anamnesis. Diagnostic knowledge proceeds from the present facts to the cause of the disease and to the past condition of the patient. Prognosis is the forecast of the patient's future condition, knowledge of what may or must happen because of the present condition. In diagnosis the physician follows from the effect to its cause, while in prognosis he foretells effects from the present cause. This cor­responds to the deductive way of arriving to a conclusion. Once the cause is revealed (e.g. an infection or an injury is discovered) the physician should know what particular effects may follow, i.e. he must know the regular reaction of the body to any particular affection. Determining effects of aetiological factors is complicated by the fact that various subjects react differently to one and the same stimulus.

The first logical process in prognosis is the ability to derive a conclusion from the examined pathology. The vital processes are very complicated and it is therefore difficult to consider all possible tendencies and regularities. Prognosis should in such cases be based on the main tendencies and

regularities.

The next stage of predicting future changes in the patient's condition is dialectical understanding of development as a contradictory process pro­ducing qualitative changes. Any pathological process causes an an­tagonistic process and both interact to enter a new stage of the disease which can end either in cure or death. The body's response to an injury is not an instantaneous response but a process occurring in time through cer­tain phases. Prognosis is based on the regularities of the development of this process. But conditions that may change these regularities are also taken into consideration. In practice the situation is even more complicated because the physician interferes with the " normal" course of the disease. Treatment should therefore also be taken into account during prognostica­tion.

The number of papers devoted to the prognosis of individual forms of diseases constantly increases and broader generalizations will probably soon appear. Advances in medicine and health care show that prognosis of diseases will be more accurate and favourable because the high reliability of diagnostic studies and observations help reveal diseases at their earlier stages and ensure greater success in their treatment. Improvement of the medical and prophylactic aid and a steady rise in the well-being of the population in the Soviet Union give grounds for this optimistic prognosis.