Introduction:
Immunocompromised patients are known to be susceptible to developing Tuberculosis (TB). Facilitation of integrated TB services at tertiary facilities for improving TB diagnosis amongst chronic kidney disease (CKD) patients (Project FOSTER) introduces uniform screening for active TB and TB infection (TBI) in selected tertiary care hospitals using Cy-TB, a new tuberculin skin-based test developed by the Serum Institute of India (Cy-TB included in National Tuberculosis Elimination Program in Oct 2023 for latent TB infection). A concordance study with the current gold standard, a QuantiFERON Gold test (IGRA), was performed to understand the efficacy of Cy-TB in this population.
Methods:
A public sector tertiary care centre was identified in New Delhi, India, with daily Nephrology out-patient (OPD) visitors between 100 to 150. A standard WHO four symptom screen W4SS symptom (Fever/ Cough/ Weight Loss/ Night Sweats), chest X-ray (CXR) and GeneXpert/smear microscopy-based screening pathway was operationalised at the facility depending on NAAT cartridge availability. An OPD-based intervention was setup wherein specialised staff were stationed inside OPD rooms to direct first-time patients towards hospital CXR facilities after obtaining informed consent. CXR negative patients were offered Cy-TB, a tuberculin-skin based test to detect latent TBI. Randomly selected patients were also offered IGRA.
Results:
In this project, we screened 2557 patients for W4SS symptoms and using CXRs. We were able to capture around 95% of the target OPD patients, including 62 glomerulonephritis (2.4%) and 37 Transplant OPD patients (1.4%). Out of these patients, 2,532 (99%) were TB negative, while 434 consented for Cy-TB. Seventy-three (16.83%) patients tested positive for Cy-TB test. Out of these patients, 80 were offered IGRA out of which 41 (51.25%) tested positive. Nineteen patients (23.75%) were both IGRA and Cy-TB positive, while 22 patients (27.5%) were IGRA negative and Cy-TB positive. The Cy-TB test has sensitivity of 46.3% and a specificity of 97.4% in diagnosing latent TB infection in CKD patients.
Conclusions:
Cy-TB has high specificity and low sensitivity in diagnosing latent TB infection in CKD. Ours is the first significant effort at quantifying the latent TB infection load among CKD patients in this region. Latent TB infection is higher among this cohort compared to general population. More work needs to be done to understand the efficacy of Cy-TB amongst CKD patients.
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.