International Journal of Infectious Diseases (Jun 2017)

The performance of the TBAg/PHA ratio in the diagnosis of active TB disease in immunocompromised patients

  • Munyemana Jean Bosco,
  • Hongyan Hou,
  • Lie Mao,
  • Xiaohui Wu,
  • Kreeti Devi Ramroop,
  • Yanfang Lu,
  • Liyan Mao,
  • Yu Zhou,
  • Ziyong Sun,
  • Feng Wang

DOI
https://doi.org/10.1016/j.ijid.2017.03.025
Journal volume & issue
Vol. 59, no. C
pp. 55 – 60

Abstract

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Objectives: The results of the T-SPOT.TB (T-SPOT) assay are reduced in immunocompromised patients with active tuberculosis (ATB), and it is difficult using T-SPOT results to distinguish ATB from latent tuberculosis infection (LTBI) in this condition. The aim of this study was to determine the performance of the TBAg/PHA ratio in T-SPOT assay in the diagnosis of ATB in immunocompromised patients. Methods: One hundred and forty three immunocompromised ATB patients and 124 LTBI individuals were diagnosed according to conventional tests and T-SPOT assay. Results: The results of T-SPOT assay are of no value in the diagnosis of ATB in immunocompromised patients. However, the number of phytohaemagglutinin (PHA) spot-forming cells (sfc) in T-SPOT assay was substantially decreased in immunocompromised ATB patients compared with that in LTBI individuals. Receiver operating characteristic (ROC) analysis revealed that a further calculation of the TBAg/PHA ratio (the larger of the ESAT-6/PHA and CFP-10/PHA) showed a better performance in distinguishing these two diseases. Using the threshold value of 0.316, the sensitivity and specificity for distinguishing immunocompromised ATB patients from LTBI individuals were respectively 79.21 and 94.05%. Conclusions: Our findings suggest that the TBAg/PHA ratio might have some significance for the diagnosis of TB disease in immunocompromised patients.

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