Atlanta Daily World

Things You Ought to Know
By W A. THOMAS, M. D.

SKIN TESTS FOR TUBERCULOSIS

Because of the large numbers of students skin tested recently, an explanation of the meaning of this test is in order. The sound moving picture "Behind the Shadows" which has been shown three times in the little theater at Spelman College, is self-explanatory but there are many who have not had the opportunity to see this picture.

In the first place the procedure of skin testing is a time saving method of screening out potential cases of tuberculosis. Nearly all people who have had a sufficiently prolonged contact with the germs of tuberculosis (tubercle bacilli) have developed what is called an infection. This means there is a focus of tuberculosis somewhere in the body. It may be very minute, so as to never cause trouble or it might be an active lesion of tuberculosis. This can never be made sure of until the X-ray picture is made and examined carefully.

It would be very expensive to first X-ray all of the students in a school, in order to find out the extent of development of disease. The skin tests will pick out those who have had an infection and who should receive the X-ray. This procedure usually eliminates little more than fifty per cent of the total number.

The tissues of a person with an Infection have been made sensitive to tuberculin. The doctors take advantage of this fact and inject into the Skin a few droplets of a dilution of emulsified dead tubercle bacilli, which has been standardized and tested. After 48 hours, the first reaction is read and recorded as one, two, three or four plus or negative. If negative the first time a stronger dilution is given and read in another forty-eight hours.

These plus marks indicate the degree of sensitivity within the tissues after the test is given and do not indicate activity of disease, as has been previously mentioned. In other words, when there is no reaction (negative) it is very likely that the person has not ever been infected with tubercle bacilli or that the sensitivity has waned because the infection was very mild.

Some individuals might be more or less sensitive than others, as indicated by the fact that some have one plus, while others have four plus reactions. The degree of sensitivity, sometimes called allergy depends upon a number of factors. Chief among these are the number of tuberculosis germs taken into the body and the amount of individual resistance or immunity which has developed. The Tuberculin Test Never Produces an Infection.

See Tuesdays World for a discussion of Resistance in Tuberculosis.