Project FOSTER: Screening for Active and Latent Tuberculosis Among Chronic Kidney Disease Patients- A Large-Scale CKD-TB Integration Study

Tuberculosis (TB) remains a major global health challenge, disproportionately affecting immunocompromised individuals. Chronic kidney disease (CKD) significantly heightens susceptibility to both active and latent TB infection (LTBI), yet systematic screening in nephrology care remains underdeveloped worldwide. Project FOSTER (Facilitation of Screening for TB among patients in Tertiary nephrology facilities for Early Recognition) represents the first study globally to implement and evaluate a comprehensive, integrated screening pathway for both active and latent TB among CKD patients in a real-world tertiary nephrology setting. The primary objectives were to estimate the prevalence of active and latent TB in CKD and to evaluate the diagnostic performance of the Cy-TB test against IGRA as the reference standard.

This cross-sectional study was conducted at a tertiary care hospital in New Delhi, India, following Institutional Ethics Committee approval. A structured three-tier screening cascade was established (Figure 1): (1) symptom screening using the WHO four-symptom screen (fever, cough, weight loss, and night sweats); (2) radiological screening by chest X-ray (CXR), performed in 94% of attendees through project-supported infrastructure; and (3) microbiological confirmation by GeneXpert/CBNAAT or smear microscopy. For latent TB detection, consenting patients underwent both Cy-TB (skin-based) and IGRA (Interferon-Gamma Release Assay) testing. Diagnostic performance of Cy-TB was evaluated taking IGRA as the gold standard. All data were analyzed descriptively to assess prevalence, concordance, sensitivity, and specificity.

Figure 1: Project FOSPTER- Patient clinical pathway

A total of 5,201 CKD patients were screened. The demographic and clinical details of the patients has been depicted in Table 1. The mean age of the cohort was 47.2 ± 13.9 years; 57.5% were male, with hypertension (42.5%) and diabetes (13.6%) being the predominant comorbidities; 3.1% were on immunosuppressive therapy. Among them, 515 (10.6%) were CXR presumptive for TB, and 49 (1%) were microbiologically confirmed (11.7% NAAT positive; 3.9% smear positive). An additional 44 (0.85%) were initiated on anti-tubercular therapy based on clinical diagnosis. The overall prevalence of active TB was 1,913 per 100,000, nearly four times higher than the general Delhi population (507.2 per 100,000). The TB diagnosis characteristics have been depicted in Table 2. For latent TB infection (LTBI), 2,141 Cy-TB and 1,235 IGRA tests were conducted, yielding 343 (16%) and 559 (45%) positives, respectively. Among 709 patients tested by both modalities, 162 were dual positive, 342 dual negative, 36 were Cy-TB(+)/IGRA(–), and 169 were Cy-TB(–)/IGRA(+). Using IGRA as the gold standard, Cy-TB demonstrated 48.9% sensitivity, 90.4% specificity, 81.8% positive predictive value, and 68.2% negative predictive value.

Table 1: Demographic and clinical profile of the patients included in the study

Table 2: TB diagnosis characteristics of the patients included in the study

Project FOSTER is the first global initiative to simultaneously quantify the burden of active and latent TB among CKD patients using an integrated, dual-modality screening pathway. The prevalence of both active TB and LTBI in CKD was markedly higher than in the general population, underscoring a significant hidden burden in this vulnerable group. The project demonstrated that comprehensive TB screening within nephrology OPDs is feasible, scalable, and effective, paving the way for integration of TB surveillance into CKD management frameworks. The Cy-TB test exhibited high specificity relative to IGRA, suggesting its utility as a cost-effective first-line screening tool in resource-limited settings. This study establishes an operational model for TB–renal program integration and provides robust evidence for policy-level adoption to strengthen TB and NCD control initiatives worldwide.