Predicting Serial TB Skin Testing Conversion or Positivity in a Low Incidence Healthcare Setting

Mark David Orvidas, Walden University


It has been established that healthcare workers are at an increased risk of testing positive on a tuberculin skin test (TST). Even though tuberculin skin testing enjoys a long history, the interpretation of the test remains controversial due to; (a) random variability in administration; (b) interpreting biologic response; (c) immunologic recall of preexisting delayed type hypersensitivity to mycobacterial antigens (boosting); or (d) new infection. Serial testing of healthcare workers is routine, so an accurate assessment of the TST is needed. This research sought to establish a checklist of risk factors that are most likely to contribute to a TST conversion by exploring the association between independent variables of age, gender, country of birth, years of employment, location of employment, and smoking status with an outcome of a TST conversion. This was a case control study of a Mayo Clinic electronic database with 123 confirmed cases of TST converted subjects and 600 controls identified in the last 15 years. These data were considered from an epidemiological triad theoretical foundation and were analyzed using bivariate (Chi-square) and multivariate regression statistics. The statistical analysis showed that the 16-34 age group (OR=19.684, p<0.0001) & the 35-44 age group (OR=6.030, p<0.0001) were significantly different when compared a reference age group of 45-94 years. Male gender (OR=3.293, p<0.0001) and high-risk job location (OR=0.193, p<0.0001) are also instrumental in the likelihood of conversion. This investigation may serve to improve the quality of care at the Mayo Clinic and represents an opportunity for positive social change at institutions with similar demographics relative to tuberculosis prevalence.