The diagnostic accuracy of Th1 (IFN-γ, TNF-α, and IL-2) and Th2 (IL-4, IL-6 and IL-10) cytokines response in AFB microscopy smear negative PTB- HIV co-infected patients

Abstract

Acid Fast Bacilli (AFB) microscopy smear remains the most widely used laboratory diagnostic technique for Pulmonary Tuberculosis (PTB) in low-and-middle income countries. Although it is highly specific, the sensitivity varies between 20-80% in immune-competent people, with only 50% case detection among HIV/TB co-infected patients, hence the need to determine the diagnostic accuracy of Th1 and Th2 cytokine response in AFB microscopy smear negative PTB-HIV co-infected patients. A total of 86 participants were recruited; 70 (81.4%) AFB microscopy smear negative and 16 (18.6%) AFB microscopy smear positive. The AFB microscopy smear negative samples were then cultured using Lowenstein Jensen Medium with 46 being culture-negative and 24 being culture-positive. Blood samples were also collected, cultured using QFT-GIT and the supernatant (plasma) harvested to evaluate cytokine profiles using Enzyme-Linked Immunosorbent Assay. IFN-γ (P < 0.001), TNF-α (P = 0.004), IL-2 (P = 0.004) and IL-4 (P = 0.009) median levels were elevated in PTB culture-positive (AFB microscopy smear negative) as compared to PTB culture-negative (AFB microscopy smear negative) participants. Finally, when Th1 cytokines (IFN-γ, TNF-α and IL-2), Th2 cytokines (IL-6 and IL-10) and T cells were included in the logistic regression fit for PTB outcome, the predictive power of discriminating between those who were AFB smear negative in the diagnosis of PTB was good with cross validated area under the curve (AUC) being 0.87 (95% CI: 0.78, 0.96). This study provides evidence for the ability of Th1 and Th2 cytokines to determine PTB status in AFB microscopy smear negative patients co-infected with HIV.

Figure 1

Predictive power of Th1 cytokines on PTB culture status among AFB microscopy smear negative. The model included INF-γ, TNF-α, IL2, CD4 (<200 vs. ≥200), and CD8 (<1000 vs. ≥1000).

Figure 2

Predictive power of Th2 cytokines on PTB culture status among AFB microscopy smear negative. The model include IL4, IL6, IL10, CD4 (<200 vs. ≥200), and CD8 (<1000 vs. ≥ 1000).

Figure 3

Predictive power of Th1 cytokines, Th2 cytokines and T-cells (CD4, and CD8) on PTB culture status among AFB microscopy smear negative. The model included IFN-γ, TNF-α, IL2, IL6, IL10, CD4 (<200 vs. ≥200), and CD8 (<1000 vs. ≥1000), but IL4 was eliminated due to inherent multicollinearity measured using variance inflation factor that was >5 units.