Case report: TB or not TB?

Probably every physician who reads this brief article will have administered the occasional TB skin test. Years ago it was requested infrequently—but in our walk-in clinic, in the last two years, I have been inundated, mainly by students from a nearby community college, with requirements for hundreds of TB skin tests. I can predict with about 99% accuracy, whether the test will be positive or negative. Immigrants from India constitute the unpredictable small number of patients who remain TB negative—even with the two-step test. The majority—with government opening up places for immigrants—are from Nigeria. As usual, the history is very helpful. I can almost forget the skin test (never given in Nigeria before coming to Canada), when the patient recalls being given an immunization with BCG—supposedly protective against TB—but quite effective in producing a positive TB skin test. Read: Case report: Summer’s endTo complete the extensive documentation required, I am obliged to administer a TB skin test—discussing the probable outcomes. The students, usually age 19 to 24, shy and female—going into a PSW program, say: “But I had a test—I had a chest X-ray.” The country of origin knew that a skin test would likely be positive. I predict a positive test—almost never wrong—and also predict the necessity for a chest X-ray—spending more of their money.The attached picture shows the dramatic result of a typical one step positive TB skin test, performed on a 20-year-old fair-skinned, healthy male student, with no illness, allergies, taking no medications, no contact with TB—but had been given BCG immunization. A ruler should have been added before taking the picture (I measure each positive test—defined as induration/erythema of 10 mm or greater) but in my measurement—usually marking the reaction with a pen—I found induration of 20 mm by 20 mm and additional erythema extending to 40 mm by 30 mm. The BCG really worked—so as usual, he needed a chest X-ray.It would be helpful and cost effective if Canadian requirements waived the skin test—just requiring the chest X-ray. This would save money and reduce anxiety and multiple physician visits. I have not yet encountered an abnormal X-ray in one of the students—already stressed by coming alone to a new country—let alone educational requirements to come. I hope that eventually—especially if the number of immigrants continues to grow—a government-sponsored free clinic could be established to assist students with testing and immunity status. I won’t even dwell on the bother that many experience in requiring blood tests to determine immunity to MMRV and hepatitis B.Robert Dickson is a family physician in Hamilton. This report is based on a real case from Dr. Dickson’s files.

Case report: TB or not TB?

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