Tuberculin Unit

Abstract: A controlled trial of BCG vaccination was conducted in 1950 in Muscogee County, Ga., and Russell County, Ala. The study population consisted of 64,136 volunteers over the age of 5 years who had satisfactory skin tests with 5 tuberculin units of purified protein derivative and whose chest photofluorograms were considered by two readers to show no significant pulmonary abnormalities. Approximately half of the nonreactors to tuberculin were vaccinated with the Tice strain of BCG by a multiple-puncture method. During a 20-year period of follow-up, 207 cases of tuberculosis were identified among the persons who had been tuberculin reactors in 1950, 36 cases were identified among the controls, and 32 cases were identified among the vaccinees. The average annual case rates per 100,000 were 47.0 for reactors, 13.4 for controls, and 12.6 for vaccinees.

Abstract: Tuberculin tests with Heaf's multiple-puncture method, as well as intradermal tests with varying strengths of old tuberculin, were carried out on 402 children with severe malnutrition. From the radiological and bacteriological findings 51 children (12.5%) were considered to have active tuberculosis. The Heaf test was positive in only 11 of these children, but the intradermal test using 100 tuberculin units was positive in a further 18. This confirms previous findings that tuberculin sensitivity is impaired in malnourished children, and suggests that a higher dose of tuberculin is more likely to elicit a positive response.

Abstract: Background: In recent decades, the prevalence of atopic diseases has risen steadily in developed countries. The reasons for this increase are not clear. It has been hypothesized that a reduction in infections and immunization programs may contribute to the increase in the prevalence of atopic diseases. We investigated the relationship between tuberculin response and atopic disease. Methods: A total of 538 (73.0%) atopic and 198 (27.0%) nonatopic children vaccinated with BCG were included in the study. All the children included in the study had neither been given BCG nor tuberculin skin-tested in the previous 6 months, nor did they have a condition known to cause anergy. All the children were given five tuberculin units PPD, and PPD indurations were recorded after 48 h. Results: The PPD induration size was 6.8±5.6 mm (mean±SD) in atopic children and 7.4±5.9 mm in nonatopic children. The difference between the two groups was not significant (P>0.05). The PPD induration sizes of children with asthma, rhinitis, and atopic dermatitis were found to be similar. The children with atopic dermatitis had lower PPD induration size, but this was not statistically significant (P>0.05). The rates of negative (<5 mm skin induration) and intermediate (5–9 mm) responses were 32.6% and 30.5% in atopic children and 30.2% and 32.4% in nonatopic children, respectively. Positive tuberculin responses (PPD≥10 mm) were recorded in 36.9% of atopic children and 37.4% of nonatopic children. Total serum IgE levels of atopic and nonatopic children were 623.35 and 46.78 IU/ml, respectively. There was no correlation between serum total IgE level and PPD induration size (r=−0.0012, P=0.737). Conclusions: We did not find any relationship between tuberculin response and atopy status later in life in BCG-immunized subjects. We need further studies to clarify the effect of BCG on the development of atopy.

Abstract: Background and objective: Detecting latent tubercular infection (LTBI) in sarcoidosis has important treatment implications. Traditionally tuberculin skin test (TST) is relied upon for this purpose. However, sarcoidosis is known to produce tuberculin anergy, which is not affected by high prevalence of tuberculosis (TB) infection. Interferon gamma release assays (IGRAs) have a higher sensitivity and specificity for detecting Mycobacterium tuberculosis (MTB) infection than the conventional TST as they utilize antigens specific for MTB complex. However, there is limited data regarding the performance of these tests in sarcoidosis, particularly in a setting of high population prevalence of LTBI.Herein, we studied the utility of IGRAs in the diagnostic work up of patients with sarcoidosis. Patients and Methods: Prospectively enrolled, biopsy-confirmed, glucocorticoid naive cases of pulmonary sarcoidosis; pulmonary and extrapulmonary TB; and, healthy controls underwent TST using 0.1 mL (1 tuberculin unit) of purified protein derivative RT23, and IGRA using QuantiFERON-TBGold In Tube™ assay (QFT) in blood. For TST an induration ≥10 mm was taken as positive. QFT was performed and interpreted as per the manufacturer’s instructions. Results:We studied 38 patients with sarcoidosis (22 men, 16 women;mean age 42.5 years), 30 patients of TB (18 pulmonary, 12 extrapulmonary) and 30 healthy controls. Patients with sarcoidosis were more likely to have a negative TST compared to healthy controls (89.5% vs. 60%, p=0.004) or TB (89.5% vs. 23.3%, p<0.001). However, QFT positivity was not significantly different in sarcoidosis compared to controls (34.2% vs. 50%, p=0.19), but was higher in TB patients as compared to sarcoidosis (60% vs. 34.2%, p=0.03). Conclusions: There is anergy to tuberculin in sarcoidosis.However, the results of QFT are not similarly affected. QFT continues to remain positive in many patients with sarcoidosis, and thus may be more accurate to detect LTBI in these patients.