Improved Serodiagnostic Sensitivity of Strip Test for Latent Tuberculosis.

INTRODUCTION: Diagnosis of Latent Tuberculosis Infection (LTBI) is difficult due to no clinical manifestations. Cases of LTBI are mostly sputum negative. The World Health Organization recommends the Tuberculin Skin Test (TST) as the current diagnostic standard for LTBI. Our previously developed serologic strip test for LTBI detection had suboptimal sensitivity. Additional Mycobacteriumtuberculosis (MTB) latency-associated antigens may improve the detection rate of LTBI.

AIM: The present study aimed to optimize sensitivity of existing strip test.

MATERIALS AND METHODS: A combination of recombinant latency proteins Rv2029c, Rv2031c, Rv2032, Rv2627c, Rv3133c, and Rv3716c was used to prepare the strips and evaluate the performance with the sera of patients in four well-classified categories: LTBI, active pulmonary TB, healthy TB contacts and other non-TB diseases.

RESULTS: A total of 91 serum samples from various clinical categories were screened with the strips. Among clinically diagnosed LTBI patients, strip test yielded a sensitivity of 75.0%. Among clinically diagnosed non-LTBI subjects, strip test yielded 88.1% specificity. The diagnostic positive and negative predictive values for strip test in reference to various clinical contexts were 77.4% and 86.7%, respectively.

CONCLUSION: Addition of the six potential latency proteins could improve the diagnostic performance of existing strip test for LTBI. The use of suitable immunodominant antigens could maximize sensitivity in the diagnosis and differentiate MTB infection status.