Pooling sputum samples for Xpert® MTB/RIF and Xpert® Ultra testing for TB diagnosis.

BACKGROUND: The use of molecular amplification as-says for TB diagnosis is limited by their costs and cartridge stocks. Pooling multiple samples to test them together is reported to have similar accuracy to individual testing and to save costs. METHODS: Two surveys of individuals with presumptive TB were conducted to assess the performance of pooled testing using Xpert® MTB/RIF (MTB/RIF) and Xpert® Ultra (Ultra). RESULTS: A total of 500 individuals were tested using MTB/RIF, with 72 (14.4%) being MTB-positive. The samples were tested in 125 pools, with 50 pools having ⩾1 MTB-positive and 75 only MTB-negative samples: 46/50 (92%, 95% CI 80.8-97.8) MTB-positive pools tested MTB-positive and 71/75 (94.7%, 95% CI 86.9-98.5) MTB-negative pools tested MTB-negative in the pooled test (agreement: 93.6%, κ = 0.867). Five hundred additional samples were tested using Ultra, with 60 (12%) being MTB-positive. Samples were tested in 125 pools, with 42 having ⩾1 MTB-positive and 83 only MTB-negative samples: 35/42 (83.6%, 95% CI 68.6-93.0) MTB-positive pools tested MTB-positive and 82/83 (98.8%, 95% CI 93.5-100.0) MTB-negative pools tested MTB-negative in the pooled test (agreement: 93.6%, κ = 0.851; P > 0.1 between individual and pooled testing). Pooled testing saved 35% (MTB/RIF) and 46% (Ultra) of cartridges. CONCLUSIONS: Pooled and individual testing has a high level of agreement and improves testing efficiency.

CONTEXTE: Le coût et les stocks de cartouches des tests d'amplification moléculaire limitent leur utilisation pour le diagnostic de la TB. Regrouper plusieurs échantillons afin de les tester en même temps aurait une précision similaire à celle des tests individuels et permettrait de réaliser des économies. MÉTHODES: Deux enquêtes ont été menées auprès de personnes avec une TB présumée afin d'évaluer la performance des tests groupés en utilisant le test Xpert® MTB/RIF (MTB/RIF) et le test Xpert® Ultra (Ultra). RÉSULTATS: Au total, 500 personnes ont été testées par test MTB/RIF, dont 72 (14,4%) étaient MTB-positives. Les échantillons ont été testés dans 125 groupes, dont 50 groupes avaient ⩾1 échantillons MTB-positifs et 75 uniquement des échantillons MTB-négatifs : 46/50 (92% ; IC 95% 80,8­97,8) groupes MTB-positifs ont été testés MTB-positifs et 71/75 (94,7% ; IC 95% 86,9­98,5) groupes MTB-négatifs ont été testés MTB-négatifs dans le test groupé (concordance : 93,6% ; κ = 0,867). Cinq cents échantillons supplémentaires ont été testés par test Ultra, dont 60 (12%) étaient MTB-positifs. Les échantillons ont été testés dans 125 groupes, dont 42 avaient ⩾1 échantillons MTB-positifs et 83 uniquement des échantillons MTB-négatifs : 35/42 (83,6% ; IC 95% 68,6­93,0) groupes MTB-positifs ont été testés MTB-positifs et 82/83 (98,8% ; IC 95% 93,5­100,0) groupes MTB-négatifs ont été testés MTB-négatifs dans le test groupé (concordance : 93,6% ; κ = 0,851 ; P > 0,1 entre les tests individuels et groupés). Les tests groupés ont permis d'économiser 35% (MTB/RIF) et 46% (Ultra) des cartouches. CONCLUSIONS: Les tests groupés et individuels présentent un niveau élevé de concordance et améliorent l'efficacité des tests.

Acute phase proteins and IP-10 as triage tests for the diagnosis of tuberculosis: systematic review and meta-analysis.

OBJECTIVES: We examined the data reported in studies for diagnostic purposes and to discuss whether their intended use could be extended to triage, as rule-in or rule-out tests to select individuals who should undergo further confirmatory tests. METHODS: We searched Scopus, PubMed and Web of Science with the terms 'acute phase proteins,' 'IP-10,' 'tuberculosis,' 'screening' and 'diagnosis,' extracted the sensitivity and specificity of the biomarkers and explored methodologic differences to explain performance variations. Summary estimates were calculated using random-effects models for overall pooled accuracy. The hierarchical summary receiver operating characteristic model was used for meta-analysis. RESULTS: We identified 14, four and one studies for C-reactive protein (CRP), interferon γ-induced protein 10 (IP-10) and alpha-1-acid glycoprotein (AGP). The pooled CRP sensitivity/specificity (95% confidence interval) was 89% (80-96) and 57% (36-65). Sensitivity/specificity were higher in high-tuberculosis-burden countries (90%/64%), HIV-infected individuals (91%/61%) and community-based studies (90%/62%). IP-10 sensitivity/specificity in TB vs. non-TB studies was 85%/63% and in TB and HIV coinfected vs. other lung conditions 94%/21%. However, IP-10 studies included diverse populations and a high risk of bias, resulting in very low-quality evidence. AGP had 86%/93% sensitivity/specificity. CONCLUSIONS: Few studies have evaluated CRP, IP-10 and AGP for the triage of symptomatic patients. Their high sensitivity and moderate specificity warrant further prospective studies exploring whether their combined use could optimize performance.