Abstract
BackgroundUrine LAM testing has been approved by the WHO for use in hospitalised patients with advanced immunosuppression. However, sensitivity remains suboptimal. We therefore examined the incremental diagnostic sensitivity of early morning urine (EMU) versus random urine sampling using the Determine® lateral flow lipoarabinomannan assay (LF-LAM) in HIV-TB co-infected patients.MethodsConsenting HIV-infected inpatients, screened as part of a larger prospective randomized controlled trial, that were treated for TB, and could donate matched random and EMU samples were included. Thus paired sample were collected from the same patient, LF-LAM was graded using the pre-January 2014, with grade 1 and 2 manufacturer-designated cut-points (the latter designated grade 1 after January 2014). Single sputum Xpert-MTB/RIF and/or TB culture positivity served as the reference standard (definite TB). Those treated for TB but not meeting this standard were designated probable TB.Results123 HIV-infected patients commenced anti-TB treatment and provided matched random and EMU samples. 33% (41/123) and 67% (82/123) had definite and probable TB, respectively. Amongst those with definite TB LF-LAM sensitivity (95%CI), using the grade 2 cut-point, increased from 12% (5–24; 5/43) to 39% (26–54; 16/41) with random versus EMU, respectively (p = 0.005). Similarly, amongst probable TB, LF-LAM sensitivity increased from 10% (5–17; 8/83) to 24% (16–34; 20/82) (p = 0.001). LF-LAM specificity was not determined.ConclusionThis proof of concept study indicates that EMU could improve the sensitivity of LF-LAM in hospitalised TB-HIV co-infected patients. These data have implications for clinical practice.
Highlights
Urine LAM testing has been approved by the WHO for use in hospitalised patients with advanced immunosuppression
lateral flow lipoarabinomannan assay (LF-LAM) sensitivity in spot versus early morning urine (EMU) Patient characteristics stratified by LAM strip results are shown in Table 1. 34% (41/123) of patients had culture/ Xpert MTB/RIF positive definite TB from sputum, while 66% (83/123) had probable-TB with other diagnostic features suggestive of TB, including clinical findings, radiological evidence suggestive of TB
Overall, the sensitivity of EMU improved from 10% (6–17) to 30% (22–38) with EMU (p < 0.001) using the grade 2 cut- point
Summary
Urine LAM testing has been approved by the WHO for use in hospitalised patients with advanced immunosuppression. There are several hurdles to diagnosis including lack of sputum production, sputum bacillary concentrations below the detection threshold of same day diagnostic tests, and atypical clinical presentation. This is further aggravated by the high frequency of extra-pulmonary (EPTB) and disseminated forms of TB with advancing immunosuppression. LAM is a point-ofcare test that is simple to use, requires no instruments, provides a result in just 25 min, and is low cost (
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