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The status of tuberculin skin testing at the Pahlavi University Medical Centre
Abstract:
Thirty-four patients with tuberculosis were skin tested with 5 tuberculin units (TU) of purified protein derivative of Mycobacterium tuberculosis (PPD). PPD supplied by Park Davis and Co., Detroit, Michigan, U.S.A. (PPD-PD) as well as PPD obtained from The Razi Institute, Hessarak, Teheran (PPD-RI) were both used for skin testing in each patient. The results indicate that 74-79% of patients with active tuberculosis have positive tuberculin reactions, that PPD-RI is a potent source of tuberculin for skin testing and that a substantial proportion of our tuberculous patients (21-26%) have negative tuberculin skin reactions.
Insights
Tuberculin skin testing using purified protein derivative (PPD) from two sources showed that most tuberculosis patients react positively. However, a significant percentage exhibited negative reactions, highlighting potential diagnostic challenges.
Area of Science:
- Immunology
- Infectious Diseases
- Microbiology
Background:
- Tuberculosis (TB) diagnosis relies on identifying Mycobacterium tuberculosis infection.
- Tuberculin skin testing (TST) is a common diagnostic tool for TB.
- Variability in TST results can impact diagnostic accuracy.
Purpose of the Study:
- To evaluate the efficacy of two different sources of purified protein derivative (PPD) for tuberculin skin testing in TB patients.
- To determine the positivity rate of TST in active tuberculosis cases.
- To assess the prevalence of negative TST reactions in patients with active tuberculosis.
Main Methods:
- Thirty-four patients diagnosed with active tuberculosis were enrolled.
- Each patient underwent skin testing with 5 tuberculin units (TU) of PPD from Parke-Davis (PPD-PD) and the Razi Institute (PPD-RI).
- Tuberculin reactions were assessed to determine positivity.
Main Results:
- Between 74% and 79% of patients with active tuberculosis demonstrated positive tuberculin reactions.
- Purified protein derivative from the Razi Institute (PPD-RI) proved to be a potent tuberculin source for skin testing.
- A notable proportion, 21-26%, of tuberculous patients exhibited negative tuberculin skin reactions.
Conclusions:
- Tuberculin skin testing with PPD is effective in identifying a majority of active tuberculosis cases.
- PPD-RI is a reliable antigen for tuberculin skin testing.
- The occurrence of negative TST in a significant minority of TB patients warrants further investigation and consideration in diagnostic strategies.