Diagnostic accuracy of the Xpert® MTB/RIF cycle threshold level to predict smear positivity: a meta-analysis.

SETTING: Xpert® MTB/RIF is the most widely used molecular assay for rapid diagnosis of tuberculosis (TB). The number of polymerase chain reaction cycles after which detectable product is generated (cycle threshold value, CT) correlates with the bacillary burden.OBJECTIVE To investigate the association between Xpert CT values and smear status through a systematic review and individual-level data meta-analysis. DESIGN: Studies on the association between CT values and smear status were included in a descriptive systematic review. Authors of studies including smear, culture and Xpert results were asked for individual-level data, and receiver operating characteristic curves were calculated. RESULTS: Of 918 citations, 10 were included in the descriptive systematic review. Fifteen data sets from studies potentially relevant for individual-level data meta-analysis provided individual-level data (7511 samples from 4447 patients); 1212 patients had positive Xpert results for at least one respiratory sample (1859 samples overall). ROC analysis revealed an area under the curve (AUC) of 0.85 (95%CI 0.82-0.87). Cut-off CT values of 27.7 and 31.8 yielded sensitivities of 85% (95%CI 83-87) and 95% (95%CI 94-96) and specificities of 67% (95%CI 66-77) and 35% (95%CI 30-41) for smear-positive samples. CONCLUSION: Xpert CT values and smear status were strongly associated. However, diagnostic accuracy at set cut-off CT values of 27.7 or 31.8 would not replace smear microscopy. How CT values compare with smear microscopy in predicting infectiousness remains to be seen.

Prevalence of tuberculosis symptoms and latent tuberculous infection among prisoners in northeastern Malaysia.

SETTING: There are currently no routine screening procedures for active tuberculosis (TB) or latent tuberculous infection (LTBI) in Malaysian prisons. OBJECTIVE: To determine the prevalence and correlates of LTBI and active TB symptoms among Malaysian prisoners with and without human immunodeficiency virus (HIV) infection using the tuberculin skin test (TST) and the World Health Organization TB symptom-based screening instrument. DESIGN: A cross-sectional survey of 266 prisoners was performed in Kelantan, Malaysia. Consenting participants underwent two-step TST and were screened for active TB symptoms. Standardized cut-offs of respectively ≥5 and ≥10 mm were used to define reactive TST among prisoners with and without HIV. Clinical and behavioral data were assessed and HIV-infected prisoners were stratified by CD4 status. RESULTS: Overall LTBI prevalence was 87.6%, with significantly lower TST reactivity among HIV-infected than non-HIV-infected prisoners (83.6% vs. 91.5%, P < 0.05); however, TB symptoms were similar (16.9% vs. 10.1%, P = 0.105). On multivariate analysis, previous incarceration (aOR 4.61, 95%CI 1.76-12.1) was the only significant correlate of LTBI. Increasing age (aOR 1.07, 95%CI 1.01-1.13), lower body mass index (aOR 0.82, 95%CI 0.70-0.96) and TST-reactive status (aOR 3.46, 95%CI 1.20-9.97) were correlated with TB symptoms. CONCLUSION: LTBI is highly prevalent, associated with previous incarceration, and suggests the need for routine TB screening on entry to Malaysian prisons.

Isoniazid preventive therapy in correctional facilities: a systematic review.

Tuberculosis (TB) remains a major cause of morbidity and mortality worldwide and the main cause of death in correctional facilities in middle- and low-income countries. Due to the closed environment and the concentration of individuals with TB-related risk factors, effective measures are required to control TB in such settings. Isoniazid preventive therapy (IPT) represents an effective and cost-effective measure. Despite international recommendations that IPT be integral to TB control, it is seldom deployed. A systematic review of interventions used to assess IPT initiation and completion in correctional facilities was conducted using published studies from two biomedical databases and relevant keywords. Additional references were reviewed, resulting in 18 eligible studies. Most (72%) studies were conducted in the United States and in jail settings (60%), with the main objective of improving completion rates inside the facility or after release. Studies that provided data about initiation and completion rates showed poor success in correctional facilities. Adverse consequences and treatment interruption ranged from 1% to 55% (median 5%) in reported studies; hepatotoxicity was the most prevalent adverse reaction. Despite its accelerating effect on the development of active TB, information on human immunodeficiency virus (HIV) status was provided in only half of the studies. Among the four studies where IPT effectiveness was assessed, the results mirror those described in community settings. Future studies require thorough assessments of IPT initiation and completion rates and adverse effects, particularly in low- and middle-income countries and where comorbid viral hepatitis may contribute significantly to outcomes, and in settings where TB and HIV are more endemic.