THE PHYSICIAN AND THE LABORATORY

The important part which the laboratory has come to play in medical science is generally accepted and appreciated, but the relation which it should bear to clinical practice remains to be satisfactorily defined. It is obvious to all clinicians of experience that the laboratory never can become, and never should become, the predominating factor in the practice of medicine, but it is equally evident that sound medicine cannot be carried on without the support of the laboratory, and that in the future the dependence of the clinic on the laboratory will probably increase rather than decrease. Among the men engaged in active medical practice, however, only a small minority can ever hope to undertake extensive laboratory work in connection with their patients, and the great majority of physicians are and will continue to be confronted by the difficult problem of their relation to this growing influence in medicine. To the teacher of medicine, whose foremost duty is to prepare his students for the practice of the future, the same problem presents itself, for the students must be thoroughly trained in the laboratory methods that will be of practical service, but not burdened with those that are highly specialized or of questionable value.

The leading exponents of clinical laboratory work are the large hospitals—especially the hospitals associated with teaching institutions—and these exert a profound effect on private medical practice, but the conditions existing in them are such as to demand a separate consideration. In such hospitals, laboratory investigations fall into one of three categories. The first includes those which belong to the field of pure research, their object being to advance the limits of our knowledge of disease. With this we have, at present, no concern. The second consists of those laboratory methods that are applied in order to obtain direct aid in the diagnosis or treatment of individual cases of disease. This often means the use of standard methods of proved and known value—methods which have received general professional acceptance—but in addition it means the use of many methods of possible value, the significance of which needs to be thoroughly tested under conditions favorable for critical control. The trying out of newly advocated measures for the diagnosis and treatment of disease must always be an important function of the larger and better equipped hospitals. Many—indeed the majority—of such methods are found to be unreliable or of little practical value, and after their status becomes established they are discarded. Very rarely a new method withstands the test of prolonged observation and proves to be of such practical significance that it can be properly advocated for general adoption. This type of hospital thus serves as the court before which all such new ideas must stand trial and it is astonishing, if not depressing, to compare the enormous amount of time and labor that is spent in gathering evidence with the comparatively meager results that pass the tests. The burden added to the hospital laboratories by such work is very great, but the importance of the function cannot be overestimated, for it filters out what is useful and protects the profession from much that is worthless.

The third category under which hospital laboratory work is carried on depends on the fact that every hospital is, or should be, an educational institution, and one of its primary duties is the instruction of all the members of the staff in the nature of disease. Many of the laboratory data, therefore, that fill the pages of carefully compiled hospital records do not have a direct diagnostic or therapeutic bearing on the individual case, but they contribute information which throws light on the pathological physiology and clarifies the disease process. In so far as the accumulation of such accessory laboratory observations is instructive to those who are studying the patients, the work is more than justified, but if, as sometimes happens, particularly with the younger members of the staff, it leads to the idea that all these observations are necessary for the proper diagnosis and treatment of any given case, the result may be most unfortunate. Properly used, such laboratory observations are enlightening and broadening; improperly used, they are blinding and narrowing. The real reason for taking an electrocardiogram on every patient with a cardiac arrhythmia is so that after one has studied the records of a large series of cases, he may understand the clinical manifestations of cardiac irregularities so well that he is able to recognize the type of arrhythmia without the electrocardiogram. His increased knowledge should, on the one hand, emancipate him from the need of the complicated apparatus in most cases, and, on the other hand, help him to appreciate the occasional case in which careful instrumental study is desirable. From this point of view, therefore, much hospital laboratory work may be regarded as of indirect significance for the individual patient, but aimed at the training of better clinicians. When, as sometimes happens, it results in the production of poor clinicians, unable to interpret disease except through the eyes of the laboratory, its purpose has failed, and failed seriously.

The physician engaged in the actual practice of medicine is directly concerned, therefore, with only a small part of the laboratory work which is carried on in the larger hospitals, for his attention must necessarily be focussed entirely on those methods which contribute immediately to the better care of his patients. The methods of the teaching clinic cannot and should not be carried into extramural practice. In the hospital all manner of tests can readily be performed in obscure or doubtful cases, but in private practice the economic factor usually restricts one to the tests which most obviously offer practical assistance. Fortunately, however—and this is apparently contrary to much present-day opinion—good medicine does not consist in the indiscriminate application of laboratory examinations to a patient, but rather in having so clear a comprehension of the probabilities and possibilities of a case as to know what tests may be expected to give information of value. Even so-called thoroughness should be tempered by reason, and the reason that must dictate the part which laboratory tests shall play in any given case must be the result of a combination of clinical experience with an understanding of the physiological significance of the available tests.

For the physician in private practice laboratory tests fall into two main classes. The first consists of those which every educated doctor should be able to carry out, and the second consists of tests which are more difficult in technique and which should be attempted only by a limited number of men who have been able to devote the time necessary to acquire specialized training. Fortunately, the first class is by far the more important of the two.

The laboratory tests which should be at the command of every practitioner of medicine are those which deal with the more important and practically useful examinations of the blood, urine, feces, gastric contents, spinal fluids, pleural and ascitic fluids. These are the tests that are customarily taught in the medical schools in the course in clinical pathology, and the instruction is usually designed to take up the laboratory methods that are absolutely necessary for good practice and those only. An experience in teaching this subject during the last seven years has emphasized the striking fact that in spite of the great contributions which the laboratory has made to clinical medicine there has been surprisingly little change in the character or number of the technical methods which are essential for good practice. In many instances the progress of medical science has resulted in a clearer, broader, and more helpful interpretation of the tests, but the actual technical procedures have not been greatly altered and they are still available to the trained man who has a minimum of laboratory apparatus. It has, indeed, been interesting to find how little new material in the way of technical procedure could justifiably be added to the course from year to year, even though the literature and the practices of various clinics were carefully followed in the attempt to keep the course up to date. The methods for the examination of the urine, for instance, are taught much as they were two decades and more ago. Certain tests, such as urea determinations, have been discarded and others are regarded as having a different significance, but the records still show the color, specific gravity, reaction, albumin and sugar content, and the microscopic examination of the sediment. These simple observations, correctly used and interpreted, are practically all that is necessary in cases of nephritis. The modern “two hour renal test” requires nothing more than determinations of volume and specific gravity, and if it is combined with the phenolsulphonephthalein test—the technique of which is entirely simple—the field is open for the study of renal function. It is far more important to understand the significance of these easy tests than it is to worry about the quantitation of blood urea or blood uric acid. The situation is much the same with regard to hematology. The technical procedures of primary value are now as they have been for years, the counting of white cells and red cells, the estimating of hemoglobin, and the preparation of stained specimens of blood. Quite recently the students at the Harvard Medical School have also been instructed in the methods of counting platelets and of staining reticulated cells, but neither of these procedures involves any essentially new technique. With these, and one or two other tests, such as coagulation time and bleeding time, the field of hematology is open. Again, the technique has been altered but little, and little has been added to it, but modern investigations have brought to it a greater significance. In the examination of the spinal fluid the cell count, which is the most important point, is merely an adaptation of the method of counting blood leucocytes, and not a new technical process. With regard to the examination of the gastric contents, body fluids, and feces, the same argument holds true; none of them involves difficult or prolonged examinations or expensive apparatus, and all of them yield information of the highest value to the man trained in their use and interpretation. Here, however, is the crux of the situation. All of these so-called routine tests are easy and consume little time in the hands of a trained man, but they are difficult, time-consuming, and of little value in the hands of an untrained man. What is really needed in the application of laboratory methods to the practice of medicine is not a knowledge of more technical procedures, but a much more exact knowledge of a few. Experience has shown that a proper degree of technical skill can rarely be obtained during the medical school course, and it should be the duty of every hospital to see that no house officer receives his diploma unless he has demonstrated an ability to perform satisfactorily all the simpler laboratory examinations and has shown a knowledge of how to use the results in the study of his patient. If every physician was so much at home with the technique of the simpler tests that it was quicker for him to apply them than to wonder whether they were worth while applying, and if he understood how to interpret these tests and gain the maximum information from them, the problem of the relation of the physician to the laboratory would be largely settled.

The second group of laboratory methods having a direct bearing on the practice of medicine consists of those which involve highly specialized technique and complicated apparatus. Electrocardiography, basal metabolism determinations, the Wassermann reaction, clinical bacteriology, and the various types of chemical analysis of the blood fall into this category. The information to be elicited from these and other analogous methods is often extremely valuable, but their application is necessary only in a comparatively limited number of cases. As a whole, these methods do not have the broad general significance and importance that characterize the simpler tests just referred to. It is, of course, highly desirable that they should be available to practicing physicians, so that they may be used in the cases in which they are particularly indicated, but fortunately there is no necessity for the great majority of physicians to bother themselves about the details of technique. This should be relegated to a small number of men who are devoting their attention to specialized fields. Simplified technical procedures, supposed to be adapted to the use of practicing physicians, are continually being advocated as substitutes for the recognized standard methods employed in performing some of these tests, but they are frequently unreliable, or reliable only in the hands of one who has a thorough knowledge of all the sources of error, so that it is far wiser to avoid them and to obtain the dependable observations of experts. The clinician may, therefore, neglect the technical side of these more elaborate tests with a clear conscience, but in so doing he should not feel that he may drop the matter entirely. If he is ever to make use of them—and this the welfare of his patients may demand—he must have an understanding of their significance and of the physiology underlying them. He must know when they are indicated and when they cannot be expected to give important evidence. A little insight into the fundamental principles of metabolism, for instance, and a recognition of the common relationship between increased heat production, pulse rate, and certain other symptoms are of the greatest help in deciding in what cases an observation of the basal metabolism may be of diagnostic significance, and in what cases it is entirely superfluous. It is much more important to know in what particular case a determination of the basal metabolism may be of value than it is to know the details of the performance of the test. Then again, the physician should be able to interpret the results of the test in the light of his individual patient. A basal metabolism which is reported as 15 per cent above normal may or may not be significant, and an electrocardiogram showing a prolonged conduction time may be due to one of several factors, but in either case the physician should not be forced to depend for the interpretation on the man who does the laboratory work and who presumably has a less intimate knowledge of the clinical condition of the patient. The clinician himself should be able to appraise the laboratory findings if the patient is to derive the greatest benefit.

It is frequently alleged that many of our medical schools and teaching hospitals are producing “laboratory men” instead of clinicians. If it is true that the graduates of these institutions enter the practice of medicine handicapped by their dependence on the laboratory, then the system of training is wrong or—what seems more probable—it is imperfectly carried out. When schools and hospitals do their full duty their graduates will have had an opportunity to study disease intensively, checking and controlling their bedside observations by a variety of exact laboratory investigations. Such an experience will enable them to correlate the clinical manifestations of disease with the underlying physiological processes, so that they can subsequently understand and interpret disease without recourse to all the laboratory procedures which were necessary in their student days. They will enter practice trained so thoroughly in a limited number of simple technical methods that they will not hesitate to use them, and they will understand all of their significance. They will also know when more complicated tests are indicated and how to interpret the results. In spite of the extraordinary influence which the laboratory has had on the development of medical science there is as yet no cause for the physician to feel that he cannot keep up with the requirements of the best modern practice. All of the more important elements are easily within his grasp. The need in clinical medicine continues to be, not for men trained in many laboratory methods but for men well grounded in a few methods—not for better technicians, but for better clinicians.