IMPORTANCE OF DARK-FIELD EXAMINATION IN EARLY DIAGNOSIS AND TREATMENT OF SYPHILIS

by M. P. Vora, M.B.B.S.

HON. CLINICAL ASSISTANT, VENEREAL DEPT., SIR J. J. HOSPITAL, BOMBAY.

The Medical Bulletin

Number. 2 of Volume No – VIII.,1940, Number. 182 of January 20 th, 1940.

Page No. 40 to 42.

Dark-field examination is a valuable means of diagnosing syphilis in its very early stage. It is a method by which one can directly observe and identify the Treponema pallidum in the living condition. Once one is familiarized with the characteristics of the Treponema pallidum it is not likely to be mistaken for anything else. Its recognition is always conclusive. Dark-field examination is very simple and can be done in a short time on a good bacteriological microscope with a special dark-field condenser. The technique is easy and can be mastered in a short time. The detection of the Treponema pallidum in the serous exudate from the chancre is pathognomonic of Lues, though failure to find at one examination does not exclude the infection. The organism, though always present, in the primary lesion may not be found at once and careful and repeated searches may be necessary. The results of the examination are accurate and compare well with other diagnostic procedures. Dark-field examination is also of considerable value in diagnosing Wassermann-negative secondary syphilis. In this examination there are not the same difficulties of interpretation, or fallacies as one has in the Wassermann reaction, which also takes some time to develop. Hence this method of diagnosis can be applied with advantage in cases of early syphilis. Great importance of early diagnosis and early institution of specific treatment in syphilis cannot be disputed; for earlier the treatment is started the greater the hope of complete cure. Besides, early diagnosis will curtail the prolonged illness and reduce the length of the courses of treatment. It also means saving some inconvenience and expenses both to the patient and the hospital. It will help to control the transmission and the spread of infection which is inevitable otherwise. Upon this will depend our best hope of eradicating the disease, an important problem in Public Health.

The tendency to wait till the Wassermann reaction proves positive is to be deplored. Usually one has to wait for a few (4 to 8) weeks before the test becomes positive- a period in which the diagnosis can be easily established in the majority of the cases by the dark-field examination. The percentage of positive Wassermann reactions increases with the age of the disease until the secondary stage is established whereas the percentage of the dark-field examinations reaches in the maximum in the second week of the appearance of the sore. In expert hands, during the second week, the results of the former have been calculated to be about 35%, while those of the latter procedure attain a figure of over 90%. “In subjecting a patient with venereal sore to a Wassermann reaction one must clearly understand that so far as the diagnosis is concerned one is employing a method which is at it’s worst precisely at a time when the dark-field examination is at its best. It means deliberate sacrifice of the patient’s chance of complete cure.”

Taking these facts into consideration and also bearing in mind the frequency of the positive results with a dark-field examination, the value of this test increases proportionately and ranks high in importance. It is very unfortunate that such a simple and reliable method of diagnosing syphilis should have sustained delay in popularization.

The Material – The follow-up of the cases studied is not very satisfactory, because several of the patients who attend the clinic sadly lack any sense of co-operation. Few patients give a proper history or follow regular treatment to completion.

A series of 120 patients, clinically diagnosed as suffering from venereal sores were subjected to dark-field examination and Wassermann reaction in the first week of their attendance in the V.D. Department of the Sir J. J. Hospital. The exact day of the appearance of the sore could not be found out in the majority of cases. The cases which were Wassermann negative in the first instance were again subjected to a Wassermann test a second time in the third week. Further follow-up was not possible because some had their treatment started, while others failed to attend. Reports of five of the cases were not available for reference. The 115 cases fall into the following groups:-

TABLE – I

TABLE – II

TABLE – III

Wassermann results with reference to the results of the Dark-field examination

TABLE – IV

The study of the above tables will show the following important points:

• Frequency of syphilitic infection: syphilis is commoner than thought. 84 cases of 115 proved positive giving percentage of 75%. Hence there is more reason to subject to dark-field examination every case of genital sore.
• Comparative efficiency of the dark-field examination over the Wassermann reaction both in the first and third week. Dark-field gives 67.7% against 13.4% in the first week and 40.7 in the third week.
• Comparative accuracy of the dark-field examination in diagnosis as shown by the figures. Only in 6 cases dark-field examination failed, while the Wassermann reaction later proved positive, this gives an error of 17.1% or slightly more if one makes an allowance for the cases which might still turn positive later on. This error is surely insignificant considering the ample compensation shown in the early diagnosis of 38 cases where the Wassermann reaction could not be of help till the end of third week. The results could have been improved still by the proper selection of the cases in the second week of the appearance of the sore and by repeated examinations. The importance of the application of simple saline dressings alone to the sores cannot be overlooked.
• Negative dark-field examination alone does not always exclude the possibility of infection; it is therefore necessary to do a Wassermann reaction where the dark-field examination is negative.

As regards the treatment, the maximum amount of treatment necessarily required in a given case will undoubtedly vary; but even in those cases who start and follow regular treatment in the sero-negative primary stage, the minimum is necessary both in amount and time. Two or three courses of specific treatment will be adequate for cure in the majority of cases instead of four minimum after all signs and symptoms have disappeared when the Wassermann reaction becomes early positive, i.e. two years’ course. A course means ten injections each of N.A.B. and Bismostab in moderate doses given regularly at weekly intervals. By this it is not meant to suggest any short or abortive form of treatment. Twenty injections each of arsenic and bismuth, probably more but not less, are fundamental to the control of syphilis in its very early stages. It could not be overemphasized that under no circumstances should the so-called abortive cure by short treatment followed by series of blood tests be considered adequate and worthy of trial; for syphilis is a relapsing disease par excellence and every consideration of its cure and prognosis must be based on this qualification.” It is this feature that renders Lues so serious.

Syphilologists should spare no efforts to impress on the minds of the patients the fact that the treatment must be pursued even though the lesion have healed and the Wassermann reactions have become negative. No case should be dismissed as cured unless and until repeated examinations of blood, cerebro-spinal fluid, skin and mucosa show persistent negative results. Cerebro-spinal fluid is examined not only for Wassermann reaction but also for increase of proteins, especially globulins and the cell-count. This is the only way to check the significant and extensive problem that confronts modern medicine.

An argument is sometimes advanced against this early treatment. It is said that it prevents ‘healthy reaction’ which is natural in the development of the disease, that it impairs the resistance of the individual and that it makes relapse or recrudescence commoner. This argument is not convincing; for there are a few cases in which a relapse is inevitable notwithstanding the fact that the cases started late treatment and followed it religiously to completion. If immunity is to develop it should do so by the time the sore appears, i.e. during the incubation period for three or more weeks, long before which the organisms completely invade the human body. Relapse- it looks reasonable- should be attributed to improper treatment, to the failure to use heavy metal with arsenic, to the tendency to attach too much importance to blood tests alone and lastly to the relapsing nature of the disease. Careful analysis of the cases will be convincing. Practically no case should relapse i.e. show signs of syphilis and become sero-positive if every case is diagnosed early, is given regularly the proper treatment and is followed up by constant observation. Relapse should become a myth and complete cure can be assured generally.

Conclusions – “The results of treatment commenced in the sero-negative primary stage are overwhelmingly superior to those begun later. It is therefore of the utmost importance to establish the diagnosis of syphilis before the advent of positive Wassermann reaction and this can only be done with certainty by finding Treponema pallidum in the serum expressed from the primary sore.” Hence dark-ground examination should be made as a routine in every case of venereal sore and the golden opportunity of treating the disease in its early and curable stage should not be lost. It would indeed be an invaluable contribution towards the treatment and relief of the syphilitics.

Acknowledgement – I am especially indebted to Dr. W. N. Weliker, Venereologist, Sir J. J. Group of Hospitals, for kindly permitting me to follow and publish the reports of the cases and Professors P.V. Gharpure and M. J. Parmanand for helping me and giving me the facilities to carry out this work and to Lt-Col. Jelal M. Shah I.M.S. for his encouragement.

REFERENCES

STOKES, Modern Syphilology.

CONYBEARE, Text Book of Medicine.

HARRISON , Venereal Diseases.

DAVID LEES, Diagnosis and Treatment of Venereal Diseases.