Lawn 2011

Study characteristics
Patient sampling	Cross‐sectional design, consecutive enrolment, prospective data collection
Patient characteristics and setting	Presenting signs and symptoms: HIV‐infected people with advanced immunodeficiency; most had 1 or more of the following TB symptoms: current cough, fever, night sweats, or weight loss Age: median 34 years (IQR 28 to 41) Sex, female: 65.4% HIV infection: 100% History of TB: 26.5% Sample size: 394 Clinical setting: HIV anti‐retroviral clinic; all participants were screened for TB Laboratory level: central Country: South Africa, Cape Town World Bank Income Classification: middle income High TB burden country: yes High MDR‐TB burden country: yes High TB/HIV burden country: yes TB incidence rate: 993 per 100,000 MDR‐TB prevalence: % MDR‐TB among new TB cases = 0.9% (Source: survey in Western Cape Province, 2002) and among retreatment cases = 4.0% (Source: survey in Western Cape Province, 2002) Prevalence of TB cases in the study: 18.3%
Index tests	Index: Xpert MTB/RIF
Target condition and reference standard(s)	Target condition: pulmonary TB Reference standard for pulmonary TB: MGIT 960 Target condition: rifampicin resistance Reference standard for rifampicin resistance: MGIT 960
Flow and timing
Comparative
Notes	This study evaluated the use of Xpert to screen HIV‐infected people with advanced immunodeficiency enrolling in antiretroviral therapy services regardless of symptoms, although most participants in the study had TB symptoms. Of 3 participants with apparent false‐positive Xpert MTB/RIF results, on follow‐up 2 had overt pulmonary and systemic symptoms suggestive of TB and improved on anti‐TB treatment. The 3rd participant was lost to follow‐up. Median CD4 cell count, 171 cells/ml; IQR 102 to 236
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Yes
		Low	Low
DOMAIN 2: Index Test Xpert MTB/RIF
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
		Low	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results for TB detection interpreted without knowledge of the results of the index test?	Yes
Were the reference standard results for rifampicin resistance detection interpreted without knowledge of the results of the index test?	Yes
		Low	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
		Low