Case report: two-step TB testing

Because our walk-in clinic is near a Community College, where a large number of young, recent immigrants (mainly female) are enrolled in courses in child care, personal support and long term residence assistance, I have seen many students requiring up-to-date immunizations and—more interestingly—skin testing for Tuberculosis. Invariably, the patients are in good health, taking no medications, but have in hand a sheaf of documents from school, requiring documentation of immune status to measles, mumps, rubella, varicella, hepatitis B—as well as a TB test. Read: Case report: A persistant rash Most patients do not have documentation of immunization in their country of origin (mostly India or the Philippines). They are sent for blood work to identify immune status. Depending on the course of study, either a one or two step TB skin test is required. A positive test (either one or two step) requires a chest x-ray (always normal). Most of the students remember being told that they were given immunization with BCG (Bacille Calmette- Guerin) as an infant. This always makes me sigh deeply, since BCG (although only marginally effective in preventing TB), quite often produces a long-standing positive TB test. Without OHIP coverage, many keep spending more money for blood work, chest x-rays etc. We do not charge for visits or required immunization if necessary. Most patients have an insurance called ”Guard Me,” which only covers acute medical problems—not the requirements of an applicant student. Read: Case report: A difficult arm lesion The background above is probably unnecessary, but not all physicians encounter a flood of young people requiring TB tests. Usually test results are clear, but not always (see picture). There is occasionally the unexpected. The picture above is the result of TB testing in a 29-year-old, healthy male with fair skin, no illnesses, and only seasonal allergies. No previous TB tests. Three weeks before the picture was taken, he was given Step 1 of a possible two-step TB skin test. Read two days later, he had a very small (about 2mm by 2mm) erythematous lesion with no induration. Hence he was recalled three weeks later for Step 2. Surprisingly, the small patch remaining from Step 1, was still present and slightly larger—still no induration. The follow-up examination of the Step 2 injection (seen below the residual result of Step 1), was dramatic. The recent lesion was a red, raised, indurated area measuring more than 20 mm by 20 mm. A chest x-ray was ordered and as usual was normal. I have rarely seen such a change from Step 1 to Step 2. I guess that is why the two-step test is requested. I thought it might be of interest to other physicians. Dr. Robert Dickson is a family physician in Hamilton. This report is based on a real case from Dr. Dickson’s files. Read: Case report: Back pain

Case report: two-step TB testing

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