Diagnostic Performance of a Novel CXCL10 mRNA Release Assay for Mycobacterium tuberculosis Infection

Abstract

One-fourth of the world’s population has been infected with Mycobacterium tuberculosis (M.tb). Although interferon-gamma release assays (IGRAs) have been shown to be valid methods for identifying M.tb infection and auxiliary methods for diagnosis of active tuberculosis (TB), lower sensitivity and higher indeterminate rate were often detected among immunosuppressed patients. IP-10 was an alternative biomarker due to the higher expression level after M.tb antigen stimulation, but whether CXCL10 mRNA (the gene that transcribes for the IP-10 protein) can be used as a target for M.tb infection diagnosis was limited. Therefore, we aimed to evaluate the performance of a novel M.tb-specific CXCL10 mRNA release assay in diagnosis of M.tb infection. Suspected TB patients and healthy controls were prospectively recruited between March 2018 and November 2019 from three hospitals in China. CXCL10 mRNA release assay and traditional interferon-gamma release assay (T-SPOT.TB) were simultaneously performed on peripheral blood. Of the 1,479 participants enrolled in the study, 352 patients with definite TB and 153 healthy controls were analyzed. CXCL10 mRNA release assay provided a sensitivity of 93.9% (95% CI = 90.8–96.2%) and a specificity of 98.0% (95% CI = 94.3–99.6%) in the diagnosis of M.tb infection, respectively, while T-SPOT.TB gave a sensitivity of 94.5% (95% CI = 91.5–96.6%) and a specificity of 100% (95% CI = 97.6–100.0%) in the diagnosis of M.tb infection, respectively. The diagnostic performance of CXCL10 mRNA release assay was consistent with T-SPOT.TB, with a total coincidence rate of 95.0% (95% CI = 93.0–96.9%) and a Cohen’s kappa value of 0.89 (0.84–0.93, p < 0.001). However, among TB patients with HIV co-infection (n = 14), CXCL10 mRNA release assay presented significantly higher positive rate [92.9% (66.1–99.8%) vs. 61.5% (31.6–86.1%), p = 0.029] than those of T-SPOT.TB. These results suggested that M.tb-specific CXCL10 mRNA was a novel and useful target in the diagnosis of M.tb infection.

Performance of T-Track® TB, a Novel Dual Marker RT-qPCR-Based Whole-Blood Test for Improved Detection of Active Tuberculosis

“…Although this study did not investigate the performance when combining CXCL10 and IFNG mRNA, it demonstrated the benefit of combining suitable mRNA markers, such as IFNG, TNFα and IL-2R or TNFα, IL-2R, CXCL9, and CXCL10, to improve TB diagnosis and differentiate Mtb infection status [15]. On the other hand, Blauenfeldt et al [37] reported sensitivity and specificity for a CXCL10 mRNA assay of 80% and 98% [25]. Recently, Pan et al reported comparable performance for a molecular CXCL10 mRNA assay vs. T-Spot.TB in 352 patients with definite TB and 153 non-TB controls, with sensitivity of 93.9% vs. 94.5% and specificity of 98.0% vs. 100% for the diagnosis of Mtb infection.…”

“…Recently, Pan et al reported comparable performance for a molecular CXCL10 mRNA assay vs. T-Spot.TB in 352 patients with definite TB and 153 non-TB controls, with sensitivity of 93.9% vs. 94.5% and specificity of 98.0% vs. 100% for the diagnosis of Mtb infection. However, in a subgroup of 14 TB patients with HIV co-infection, the molecular CXCL10 mRNA test showed a significantly higher positive rate (92.9%) than T-Spot.TB (61.5%; p = 0.029) [37]. Varying stimulation protocols, such as distinct stimulants or stimulation times, may explain the differences in the performance of the molecular tests described in the literature.…”

Evaluation of the IP-10 mRNA release assay for diagnosis of TB in HIV-infected individuals

“…Our previous study has confirmed that the IP-10 mRNA can be effectively used as a target for the diagnosis of M.tb infection in HIV-infected individuals, as evidenced by its higher sensitivity and lower indeterminate rate of the detection (Pan et al, 2021;Pan et al, 2022). However, whether it can be used as an auxiliary method for diagnosis of TB, should also be validated in a larger cohort.…”

“…This multicenter, prospective study was performed across five hospitals in China, including the Shanghai Public Health Clinical Center (Eastern), the Beijing Chest Hospital (Eastern), the Beijing Youan Hospital (Eastern), the Gansu Provincial Infectious Disease Hospital (Western) and the Eighth Affiliated Hospital, Xinjiang Medical University (Western). According to the positive rate of IP-10 mRNA release assay (92.9%) and IGRA (61.5%) among HIVcoinfected patients in our previous study (Pan et al, 2022), we performed sample size calculation and the final minimum sample size of TB/HIV co-infected patients was 143. Therefore, we prospectively and continuously recruited the suspected HIV/TB co-infected patients from the five participating hospitals and ended when the HIV/TB co-infected patients in case group was enough, between May 2021 and May 2022.…”

“…The relative amount of IP-10 mRNA in each tube (with or without antigens) was calculated separately. The test results were classified as indeterminate, negative, or positive according to the previously published criteria (Pan et al, 2022). Briefly, the test result was positive if the relative amount of IP-10 mRNA (DCT) in M.tb antigen tube minus that in Nil control tube was ≤ -1.04; the test result was negative if the DCT value in M.tb antigen tube minus that in Nil control tube was > -1.04 and the DCT value in mitogen tube minus that in Nil control tube was ≤ -1.2; and 'indeterminate' was defined as that the DCT value in M.tb antigen tube minus that in Nil control tube was > -1.04 and the DCT value in mitogen tube minus that in Nil control tube was > -1.2.…”