Validation of a Clinical-Radiographic Score to Assess the Probability of Pulmonary Tuberculosis in Suspect Patients with Negative Sputum Smears

Abstract

BackgroundClinical suspects of pulmonary tuberculosis in which the sputum smears are negative for acid fast bacilli represent a diagnostic challenge in resource constrained settings. Our objective was to validate an existing clinical-radiographic score that assessed the probability of smear-negative pulmonary tuberculosis (SNPT) in high incidence settings in Peru.Methodology/Principal FindingsWe included in two referral hospitals in Lima patients with clinical suspicion of pulmonary tuberculosis and two or more negative sputum smears. Using a published but not externally validated score, patients were classified as having low, intermediate or high probability of pulmonary tuberculosis. The reference standard for the diagnosis of tuberculosis was a positive sputum culture in at least one of 2 liquid (MGIT or Middlebrook 7H9) and 1 solid (Ogawa) media. Prevalence of tuberculosis was calculated in each of the three probability groups.684 patients were included. 184 (27.8%) had a diagnosis of pulmonary tuberculosis. The score did not perform well in patients with a previous history of pulmonary tuberculosis. In patients without, the prevalence of tuberculosis was 5.1%, 31.7% and 72% in the low, intermediate and high probability group respectively. The area under de ROC curve was 0.76 (95% CI 0.72–0.80) and scores ≥6 had a positive LR of 10.9.Conclusions/SignificanceIn smear negative suspects without previous history of tuberculosis, the clinical-radiographic score can be used as a tool to assess the probability of pulmonary tuberculosis and to guide the decision to initiate or defer treatment or to requesting additional tests.

Scoring systems using chest radiographic features for the diagnosis of pulmonary tuberculosis in adults: a systematic review

“…After full-text review, 174 articles were excluded for various reasons and 13 articles (all observational studies) were included in the systematic review ( fig. 1) [20][21][22][23][24][25][26][27][28][29][30][31][32].…”

“…Studies that only included patients with possible PTB who were found to be sputum smear negative We identified five studies in this category [26][27][28][29][30]. Four studies were conducted in an inpatient setting for the purpose of determining a clinical rule for respiratory isolation [26,27,29,30]; while one study was performed in an outpatient setting [28] (table 1).…”

“…Four studies were conducted in an inpatient setting for the purpose of determining a clinical rule for respiratory isolation [26,27,29,30]; while one study was performed in an outpatient setting [28] (table 1). As with the previously described set of studies that included all patients with possible PTB, in the univariate analysis the most common radiographic features across studies found to be associated with PTB were upper lobe infiltrates (pooled DOR 3.57, 95% CI 2.38-5.37; five studies) ( fig.…”

“…Of the 13 included studies, 12 studies involved scoring systems that combined clinical and radiographic features [20][21][22][23][24][25][26][27][28][29][30][31] and one study involved validation of 13 clinical prediction rules for inpatient respiratory isolation [32]. This study was included as it retrospectively applied prediction rules from six studies identified by our systematic review to a group of eligible participants with symptoms suggestive of PTB.…”

“…This study also tested rules that were derived from seven other studies, which were excluded from our systematic review as they did not satisfy our reference standard [33,34] or did not use specific features visualised on the chest radiograph as part of the scoring system [35][36][37][38][39]. Seven studies included all patients with possible PTB [20][21][22][23][24][25]32], five studies included patients with possible PTB who were found to have negative sputum smears [26][27][28][29][30], and one study specifically excluded PLWH [31]. Nine studies were performed in high-income countries.…”