Test characteristics and potential impact of the urine LAM lateral flow assay in HIV-infected outpatients under investigation for TB and able to self-expectorate sputum for diagnostic testing

Table 2 Key diagnostic accuracy measures of LAM (grade 2 cut-point), sputum Xpert MTB/RIF or smear microscopy alone or in combination for culture-confirmed versus culture-negative pulmonary tuberculosis amongst HIV-infected (and refused testing) patients stratified by CD4 cell count

Diagnostic (s)		Sensitivity		Specificity
	n/N	% (95% CI)	n/N	% (95% CI)
LAM alone^a
HIV-infected	41/181	22.7 (16.6-28.7)	361/388	93.0 (90.5-95.6)
CD4 ≤ 100 cells/mm^{3 b}	14/46	30.4 (17.1-43.7)	70/75	93.3 (87.7-99.0)
CD4 > 100 cells/mm³	23/126	18.3 (12.5-25.9)	257/274	93.8 (90.3-96.1)
Xpert MTB/RIF alone
HIV-infected	70/92	76.1 (67.4-84.8)	182/196	92.9 (88.4-95.7)
CD4 ≤ 100 cells/mm³	16/21	76.2 (58.0-94.4)	36/40	90.0 (80.7-99.3)
CD4 > 100 cells/mm³	47/63	74.6 (62.7-83.7)	130/138	94.2 (89.0-97.0)
Smear alone
HIV-infected	39/89	43.8 (34.0-54.2)	179/192	93.2 (88.8-96.0)
CD4 ≤ 100 cells/mm³	9/25	36.0 (17.2-54.8)	31/35	88.9 (78.6-99.1)
CD4 > 100 cells/mm³	30/63	47.6 (35.8-59.7)	129/136	94.9 (89.8-97.5)
Xpert MTB/RIF and LAM combined^c
HIV-infected	72/92	78.3 (69.8-86.7)	169/196	86.2 (81.4-91.0)
CD4 ≤ 100 cells/mm³	18/21	85.7 (70.7-100.1)	35/40	87.5 (77.3-97.7)
CD4 > 100 cells/mm³	47/63	74.6 (62.7-83.7)	121/138	87.7 (81.2-92.2)
Smear and LAM combined^c
HIV-infected	50/89	56.2 (45.9-66.5)	172/192	89.6 (85.3-93.9)
CD4 ≤ 100 cells/mm³	11/25	44.0 (24.5-63.5)	28/35	80.0 (66.7-93.3)
CD4 > 100 cells/mm³	38/63	60.3 (48.0-71.5)	125/136	91.9 (86.1-95.4)

^a14/583 HIV-infected and test refused patients had no reference standard result (see Fig. 1) and therefore a total of 569 patients were used for evaluation of urinary LAM performance
^b48/569 HIV-infected patients with LAM test results missing CD4 cell count data. For no diagnostic accuracy measure did any of the diagnostic tests, either alone or in combination, performed significantly better in CD4 ≤ 100 cells/mm³ compared to CD4 > 100 cells/mm³ (p > 0.05)
^cEither test positive is considered as a “positive” result

ISSN: 1471-2334