Influential Factors of the Indeterminate Results Tested by QuantiFERON-TB Gold In-Tube (QFT-IT) Assay for Diagnosing TB Infection in HIV-Infected Patients.

BACKGROUND

QuantiFERON-TB Gold In-Tube test (QFT-IT) is a recommended method for diagnosing TB in HIV-infected patients. However, the rate of indeterminate results is higher than that in HIV-uninfected patients. Our previous study showed that the CD4 cell count was an important influential factor for the indeterminate results of QFT-IT. Whether other influential factors affect the QFT-IT results was unclear.

METHODS

In this paper, 98 HIV-infected patients with suspected TB infection were enrolled and the plasma of peripheral blood was collected for QFT-IT. The relationship between the CD4 T-cell count, lymphocyte count, lymphocyte percentage, and the results of QFT-IT were analyzed.

RESULTS

All patients who have the clinical symptoms of TB including fever and productive cough and were later confirmed by other assays including the sputum culture and chest radiography (n = 8) tested as QFT-positive (positive rate 100%). The other 90 patients without clinical symptoms tested as negative (n = 51), indeterminate (n = 33), and positive (n = 6). The lymphocyte count and the lymphocyte percentage as well as the CD4 T-cell count were significant higher in the positive group and negative group than in the indeterminate group (p < 0.05, for all).

CONCLUSIONS

The QFT-IT could be a potential, simple, and feasible method for diagnosing and screening TB in HIV-infected patients. In addition, the CD4 T-cell count, the lymphocyte count, and the lymphocyte percentage were influential factors of the indeterminate results of QFT-IT.