The Bandim TBscore - reliability, further development, and evaluation of potential uses

Abstract

Background: The tuberculosis (TB) case detection rate has stagnated at 60% due to disorganized case finding and insensitivity of sputum smear microscopy. Of the identified TB cases, 4% die while being treated, monitored with tools that insufficiently predict failure/mortality. Objective: To explore the TBscore, a recently proposed clinical severity measure for pulmonary TB (PTB) patients, and to refine, validate, and investigate its place in case finding. Design: The TBscore's inter-observer agreement was assessed and compared to the Karnofsky Performance Score (KPS) (paper I). The TBscore's variables underlying constructs were assessed, sorting out unrelated items, proposing a more easily assessable TBscoreII, which was validated internally and externally (paper II). Finally, TBscore and TBscoreII's place in PTB-screening was examined in paper III. Results: The inter-observer variability when grading PTB patients into severity classes was moderate for both TBscore (kW=0.52, 95% CI 0.46-0.56) and KPS (KW=0.49, 95% CI 0.33-0.65). KPS was influenced by HIV status, whereas TBscore was unaffected by it. In paper II, proposed TBscoreII was validated internally, in Guinea-Bissau, and externally, in Ethiopia. In both settings, a failure to bring down the score by ≥25% from baseline to 2 months of treatment predicted subsequent failure (p=0.007). Finally, in paper III, TBscore and TBscoreII were assessed in health-care-seeking adults and found to be higher in PTB-diagnosed patients, 4.9 (95% CI 4.6-5.2) and 3.9 (95% CI 3.8-4.0), respectively, versus patients not diagnosed with PTB, 3.0 (95% CI 2.7-3.2) and 2.4 (95% CI 2.3-2.5), respectively. Had we referred only patients with cough >2 weeks to sputum smear, wewould have missed 32.1% of the smear confirmed cases in our cohort.ATBscoreII >=2 missed 8.6%. Conclusions: TBscore and TBscoreII are useful monitoring tools for PTB patients on treatment, as they could fill the void which currently exists in risk grading of patients. They may also have a role in PTB screening; however, this requires our findings to be repeated elsewhere. © 2014 Frauke Rudolf.