Author:
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Ssengooba, Willy; Respeito, Durval; Mambuque, Edson; Blanco, Silvia; Bulo, Helder; Mandomando, Inácio; Jong, Bouke C. de; Cobelens, Frank; García-Basteiro, Alberto L.
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Abstract:
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INTRODUCTION: Early diagnosis and initiation to appropriate
treatment is vital for tuberculosis (TB) control. The
XpertMTB/RIF (Xpert) assay offers rapid TB diagnosis and
quantitative estimation of bacterial burden through Cycle
threshold (Ct) values. We assessed whether the Xpert Ct value is
associated with delayed TB diagnosis as a potential monitoring
tool for TB control programme performance. MATERIALS AND
METHODS: This analysis was nested in a prospective study under
the routine TB surveillance procedures of the National TB
Control Program in Manhica district, Maputo province,
Mozambique. Presumptive TB patients were tested using smear
microscopy and Xpert. We explored the association between Xpert
Ct values and self-reported delay of Xpert-positive TB patients
as recorded at the time of diagnosis enrolment. Patients with
>60 days of TB symptoms were considered to have long delays.
RESULTS: Of 1,483 presumptive TB cases, 580 were diagnosed as TB
of whom 505 (87.0%) were due to pulmonary TB and 302 (94.1%)
were Xpert positive. Ct values (range, 9.7-46.4) showed a
multimodal distribution. The median (IQR) delay was 30 (30-45)
days. Ct values showed no correlation with delay (R2 = 0.001, p
= 0.621), nor any association with long delays: adjusted odds
ratios (AOR) (95% confidence interval [CI]) comparing to >28
cycles 0.99 (0.50-1.96; p = 0.987) for 23-28 cycles, 0.93
(0.50-1.74; p = 0.828) for 16-22 cycles; and 1.05 (0.47-2.36; p
= 0.897) for <16 cycles. Being HIV-negative (AOR [95% CI]),
2.05 (1.19-3.51, p = 0.009) and rural residence 1.74 (1.08-2.81,
p = 0.023), were independent predictors of long delays.
CONCLUSION: Xpert Ct values were not associated with patient
delay for TB diagnosis and cannot be used as an indicator of TB
control program performance. |