The diagnostic value of hydroxyproline combined with tuberculosis infection T lymphocyte spot assay in pulmonary tuberculosis.

Background: Tuberculosis (TB) is an infectious disease which has long threatened human health, and new molecular diagnostic markers for its diagnosis are urgently needed. The study was designed to analyze the expression of hydroxyproline (HYP) in different specimens of pulmonary TB (PTB) and assess its auxiliary diagnostic value alone or in combination with the TB infection T lymphocyte spot assay (TSPOT.TB).

Methods: According to the inclusion criteria, 43 healthy controls (HCs) and 39 patients with nontuberculous general respiratory diseases were included as the respiratory control (RC) group, while 42 patients with newly treated TB were included as the PTB group. The expression of HYP in serum, urine, and bronchoalveolar lavage fluid (BALF) was detected with a HYP detection kit. Correlation analysis was used to detect the correlation of HYP and clinical indicators. Receiver operating characteristic (ROC) curve analysis was used to determine the sensitivity and specificity of HYP in diagnosing TB, both when used alone and in combination with TSPOT.TB.

Results: The expression of HYP in serum of patients with TB was significantly increased as compared to that in controls (P=0.03), but there was no significant difference in the expression of HYP in urine (P>0.05). Compared with the general pneumonia control group, the expression of HYP in BALF of the PTB group was significantly increased (P<0.001). HYP expression in serum was positively correlated with C-reactive protein (CRP) level (r=0.4661, P=0.002), neutrophil (r=0.3338, P=0.03) and monocyte count (r=0.3462, P=0.02), and was negatively correlated with serum albumin expression (r=-0.3575, P=0.02). The expression of HYP in urine was positively correlated with neutrophil count (r=0.3508, P=0.02), neutrophil percentage (r=0.3804, P=0.047), and monocyte count (r=0.3263, P=0.04) but was negatively correlated with serum albumin expression (r=-0.4031, P=0.008). The expression of HYP in BALF was positively correlated with CRP (r=0.3652, P=0.02) but not with other indexes (P>0.05). ROC curve analysis indicated that the sensitivity, specificity, and area under the curve (AUC) of blood HYP were 66.67%, 72.09%, and 0.6481, respectively, while those of its combined diagnosis with TSPOT.TB were 78.57%, 96.77%, and 0.8690, respectively. The sensitivity, specificity, and AUC of HYP in BALF were 67.74%, 64.29%, and 0.7435, respectively, while those of its combined diagnosis with TSPOT.TB were 78.59%, 93.55%, and 0.8606, respectively.

Conclusions: The expression of HYP in the serum and BALF of patients with PTB was higher than that of control group, and the expression of HYP was correlated with some clinical indicators. HYP demonstrated good sensitivity and specificity for the primary screening of PTB and higher sensitivity and specificity in the diagnosis of HYP when combined with TSPOT.TB. It may thus have certain value for auxiliary diagnosis in clinic.