Performance of an algorithm based on WHO recommendations for the diagnosis of smear‐negative pulmonary tuberculosis in patients without HIV infection

Abstract

Summaryobjective To evaluate the performance of an algorithm based on WHO recommendations for diagnosis of smear-negative pulmonary tuberculosis in HIV-negative patients.methods We recruited HIV-negative patients with clinical suspicion of tuberculosis who had had three negative sputum smears in Lima, Peru. All included subjects underwent a complete anamnesis, physical examination and chest X-ray, and had a sputum specimen cultured in Ogawa, Middlebrook 7H9 media and MGITÒ. We applied an algorithm based on WHO recommendations to classify patients as having tuberculosis or not. The diagnostic performance of the algorithm was evaluated comparing its results against the reference standard of a positive culture for M. tuberculosis in either of the media used.results A total of 264 of the 285 patients included (92.6%) completed evaluation and follow up. Of these, 70 (26.5%) had a positive culture for M. tuberculosis. Clinical response to a broad spectrum course of antibiotics was good in 32 of these 70 patients (45.7; 95%CI 34.0-57.4%). Overall, the algorithm attained a sensitivity of 22.9% (95% CI 13.1-32.7%) and a specificity of 95.4 % (95% CI 92.4-98.3%) compared to culture results. The positive likelihood ratio was 4.93 and the negative likelihood ratio was 0.81.conclusions The sensitivity and negative likelihood ratio of the algorithm is poor. It should be reevaluated, and possibly adapted to local circumstances before further use. The clinical response to an antibiotic trial is the most important component to reassess. We also suggest considering performing chest X-ray earlier in the diagnostic work-up.

Performance of the 2007 WHO Algorithm to Diagnose Smear-Negative Pulmonary Tuberculosis in a HIV Prevalent Setting

“…In Homa Bay, the clinical-radiological algorithm led to a high proportion of TB cases missed and a high proportion of patients overtreated. Our study is in line with most of the studies carried out in similar settings [6], [22], [25], [30] which have shown low algorithm sensitivity ranging from 23% to 59%. However, sensitivities of 80–95% have also been reported [23], [24].…”

Research on Implementation of Interventions in Tuberculosis Control in Low- and Middle-Income Countries: A Systematic Review

“…Two studies compared predefined rule-in algorithms against standard practice, both in a before–after design: one compared the proportions of smear-positive diagnoses before and after introducing a locally developed clinical algorithm in Ethiopia using routine notification data [21], and the other study compared hospitalization and mortality among severely ill HIV-infected individuals suspected to have TB, before and after introducing the WHO algorithm for diagnosis of smear-negative TB [22] in routine practice in South Africa [23]. Four other recent studies evaluated the 2007 WHO algorithm for ruling in smear-negative TB; one compared it to the 2003 WHO algorithm in Uganda [24], and the remaining three (from Brazil, Cambodia, and South Africa) used a non-comparative cross-sectional or retrospective design [25]–[27]. One study evaluated the most recent WHO-recommended algorithm for ruling out TB in HIV-infected individuals in Vietnam using a non-comparative design [28].…”

Algorithm for the diagnosis of smear‐negative pulmonary tuberculosis in high‐incidence resource‐constrained settings

“…The clinical prediction rule, based on symptoms and chest X-ray findings, which we use in the algorithm has been evaluated previously as stand-alone tool (Soto et al 2011a). It identified well patients with high and low probabilities of SNPT and should permit to rationalise the use of liquid culture by reserving it for suspects with intermediate probability.…”

“…Among them, over 10% had a final diagnosis of SNPT. Improvement must be viewed with caution and does not permit to exclude the disease, as also demonstrated in an evaluation of the current WHO algorithm for HIV-negative smear-negative SNPT suspects (Soto et al 2011b). In the present study, all SNPT patients could eventually be put on antituberculous treatment, but if culture is not performed in suspects who improve under broad-spectrum antibiotics, they are lost or their diagnosis will be seriously delayed.…”