Incremental yield of including Determine-TB LAM assay in diagnostic algorithms for hospitalized and ambulatory HIV-positive patients in Kenya

Background

Determine-TB LAM assay is a urine point-of-care test useful for TB diagnosis in HIV-positive patients. We assessed the incremental diagnostic yield of adding LAM to algorithms based on clinical signs, sputum smear-microscopy, chest X-ray and Xpert MTB/RIF in HIV-positive patients with symptoms of pulmonary TB (PTB).

Methods

Prospective observational cohort of ambulatory (either severely ill or CD4<200cells/mu l or with Body Mass Index

Results

Among 474 patients included, 44.1% were severely ill, 69.6% had CD4<200cells/mu l, 59.9% had initiated ART, 23.2% could not produce sputum. LAM, smear-microscopy, Xpert and culture in sputum were positive in 39.0% (185/474), 21.6% (76/352), 29.1% (102/350) and 39.7% (92/232) of the patients tested, respectively. Of 156 patients with confirmed TB, 65.4% were LAM positive. Of those classified as non-TB, 84.0% were LAM negative. Adding LAM increased the diagnostic yield of the algorithms by 36.6%, from 47.4% (95% CI: 39.4- 55.6) to 84.0% (95% CI: 77.3-89.4%), when using clinical signs and X-ray; by 19.9%, from 62.2% (95% CI: 54.1-69.8) to 82.1% (95% CI: 75.1-87.7), when using clinical signs and microscopy; and by 13.4%, from 74.4% (95% CI: 66.8-81.0) to 87.8% (95% CI: 81.6-92.5), when using clinical signs and Xpert. LAM positive patients had an increased risk of 2-months mortality (aOR: 2.7; 95% CI: 1.5-4.9).

Conclusion

LAM should be included in TB diagnostic algorithms in parallel to microscopy or Xpert request for HIV-positive patients either ambulatory (severely ill or CD4