Use of an enzyme-linked immunospot assay for diagnosing latent tuberculosis infection in rheumatic diseases / 中华风湿病学杂志

ABSTRACT

Objective To compare the efficacy of the conventional PPD skin test and a new enzymelinked immunospot assay(TSPOT-TB)for diagnosing latent tuberculosis infection(LTBI)in patients with rheumatic diseases.Methods Two hundred and sixty rheumatic patients were enrolled,and all were screened for LTBI based on clinical history,chest X-ray,PPD skin test or TSPOT.Results The positive rate of TSPOT assay was 24.1%and that of PPD skin test was 39.4%.The overall concordance rate between the 2tests was 61.0%.Among PPD negative patients (n=149).29 were TSPOT(+)(19.5%).Among PPD(+)patients(n=98),69 were TSPOT(-)(70.0%).The patients who got BCG vaccination or had history of tuberculosis infection showed a significantly higher rate of positive result of PPD skin test than those who did not (P<0.05 or P<0.01).While in TSPOT assay,the BCG vaccination or history of tuberculosis infection did not show influence on TSPOT results(P>0.05).Of the 127 patients who received biological agents after screening for LTBI,9 patients were pretreated with isoniazide.Twenty-seven patients stopped biological agent treatment because of the positive results of PPD or TSPOT.Twenty three patients who had positive PPD but negative TSPOT results received biological agent treatment without isoniazide,and none of them developed active tubereulosis after 6 to 18 months of follow-up.Conclusion BCG vaccination affects the result of PPD test in rheumatic patients,but has no influence on TSPOT results.The infection rate of latent tuberculosis of rheumatic patients in our research is 23.8%detected by TSPOT.