| Popis: |
When a large, unselected and statistically valid number of modern city dwellers is tested by intracutaneous injection of tuberculin in the usual test dose of about of a milligram of Old Tuberculin Koch (0.1 cm. of a dilution of 1: 5,000 OTK), some will react and some will not. If such testing is done nowadays on large groups distinguished by ages, the results are likely to be approximately as follows: Between birth and 2 years (in infancy), almost all will fail to react. Between 2 and 10 years, many fewer will react than not. Between 10 and 20 years, reactors and non-reactors will be nearly equal in number. Between 20 and 40 years, there will be significantly more reactors than nonreactors. Between 40 years and extreme old age, the number of non-reactors will be greater in proportion to reactors than in the 20—40 year group. Without citing exact figures in the interest of brevity, these ratios, as a trend, are nevertheless submitted to reflect the true situation in New York City at least, and are graphically presented for emphasis in Chart I. The ratios correspond to the actual figures found by Pascher and Sulzberger (1) in a study of the age incidence of positive tuberculin reactions in the New York Skin and Cancer Unit Clinic. Reference may also be made to the bibliography of that article for other studies that substantiate the trend. Tuberculin testing can be refined by employing the serial dilution method as practised by dermatologists since its introduction by J. Jadassohn. When low concentrations of tuberculin are used, down to j, mg., it will be found that some of the positive reactors still react; and with greater concentrations, up to several milligrams, some of the seeming non-reactors to mg. will be found to begin to react at or 1 mg. But some others of the non-reactors, almost all infants and quite a few adults, will not react to any reasonable concentration or milligrammage of tuberculin. In other words, some persons are practically completely insensitive or anergic to tuberculin. |
