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Clinical utility of a commercial LAM-ELISA assay for TB diagnosis in HIV-infected patients using urine and sputum samples

Dheda, Keertan and Davids, Virginia and Lenders, Laura and Roberts, Teri and Meldau, Richard and Ling, Daphne and Brunet, Laurence and Zyl-Smit, Richard N. van and Peter, Jonathan and Green, Clare and Badri, Motasim and Sechi, Leonardo Antonio and Sharma, Surendra and Hoelscher, Michael and Dawson, Rodney and Whitelaw, Andrew and Blackburn, Jonathan and Pai, Madhukar and Zumla, Alimuddin (2010) Clinical utility of a commercial LAM-ELISA assay for TB diagnosis in HIV-infected patients using urine and sputum samples. PLoS One, Vol. 5 (3), e9848. ISSN 1932-6203. Article.

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DOI: 10.1371/journal.pone.0009848

Abstract

Background. The accurate diagnosis of TB in HIV-infected patients, particularly with advanced immunosuppression, is difficult. Recent studies indicate that a lipoarabinomannan (LAM) assay (Clearview-TB®-ELISA) may have some utility for the diagnosis of TB in HIV-infected patients; however, the precise subgroup that may benefit from this technology requires clarification. The utility of LAM in sputum samples has, hitherto, not been evaluated.
Methods. LAM was measured in sputum and urine samples obtained from 500 consecutively recruited ambulant patients, with suspected TB, from 2 primary care clinics in South Africa. Culture positivity for M. tuberculosis was used as the reference standard for TB diagnosis.
Results. Of 440 evaluable patients 120/387 (31%) were HIV-infected. Urine-LAM positivity was associated with HIV positivity (p = 0.007) and test sensitivity, although low, was significantly higher in HIV-infected compared to uninfected patients (21% versus 6%; p<0.001), and also in HIV-infected participants with a CD4 <200 versus >200 cells/mm3 (37% versus 0%; p = 0.003). Urine-LAM remained highly specific in all 3 subgroups (95%–100%). 25% of smear-negative but culture-positive HIV-infected patients with a CD4 <200 cells/mm3 were positive for urine-LAM. Sputum-LAM had good sensitivity (86%) but poor specificity (15%) likely due to test cross-reactivity with several mouth-residing organisms including actinomycetes and nocardia species.
Conclusions. These preliminary data indicate that in a high burden primary care setting the diagnostic usefulness of urine-LAM is limited, as a rule-in test, to a specific patient subgroup i.e. smear-negative HIV-infected TB patients with a CD4 count <200 cells/mm3, who would otherwise have required further investigation. However, even in this group sensitivity was modest. Future and adequately powered studies in a primary care setting should now specifically target patients with suspected TB who have advanced HIV infection.

Item Type:Article
ID Code:3839
Status:Published
Refereed:Yes
Uncontrolled Keywords:TB diagnosis, HIV-infected patients, LAM-ELISA
Subjects:Area 06 - Scienze mediche > MED/07 Microbiologia e microbiologia clinica
Divisions:001 Università di Sassari > 01 Dipartimenti > Scienze biomediche
Publisher:Public Library of Science
ISSN:1932-6203
Copyright Holders:© 2010 Dheda et al.
Deposited On:07 May 2010 13:00

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