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Diagnosis of active tuberculosis by detection of urinary lipoarabinomannan (uLAM) fromM easuring microbial antigens excreted into urine offers an attractive approach to diagnose acute infections (1-3). While the diagnostics of tuberculosis (TB) is challenging, an appealing approach is to detect urinary lipoarabinomannan (uLAM), the major structural component of the outer cell wall, shed into the environment by replicating, metabolically active, or degrading mycobacteria (4-6). Several publications have reported the use of the Clearview TB enzyme-linked immunosorbent assay (ELISA) (Inverness Medical Innovations, Bedford, United Kingdom) (7-12) or MTB LAM ELISA (Chemogen, Portland, ME) (13-17) to detect uLAM. The assay has almost invariably been found to have better sensitivity for cases with advanced HIV infection than for cases without HIV (7,8,11,12,16,17). This has been explained by the progressively increasing bacillary burden in TB-positive and HIV-positive (TB ϩ /HIV ϩ ) patients after the profound loss of CD4 ϩ T cells and the inability to restrict mycobacterial growth, which results in heavy antigenemia and excretion of larger amounts of LAM into urine (8,11,12,15).The present study was carried out to (i) examine whether concentrating urine will improve the analytical sensitivity of the Clearview TB ELISA in TB ϩ /HIV Ϫ patients, (ii) estimate the quantities of LAM excreted, (iii) look into the factors affecting analytical performance, and (iv) investigate the correlation of LAM detection rates in concentrated and nonconcentrated urine with sputum staining.Midstream urine samples were collected in Finland ( F ) and Taiwan ( T ) from adult patients with active pulmonary TB (P F -TB, n ϭ 28, and P T -TB, n ϭ 17) or extrapulmonary TB (EP F -TB, n ϭ 7, and EP T -TB, n ϭ 3), miliary TB (n ϭ 2), latent TB (LTBI; n ϭ 15), or treated TB (n ϭ 4) infections, from disease control groups (n ϭ 60), and from healthy volunteers (n ϭ 101). The clinical and demographic details on enrolled groups are presented in Text S1 and Table S2 When optimizing the assay, we found that LAM dissolved in urine produced higher optical densities (ODs) than that dissolved in water, and a wide range of pHs (Ͼ3) was tolerable without deterioration. The calibration curves were prepared as described in Text S3 in the supplemental material; the effect of concentration on the ODs is shown in Fig. S4. The theoretical analytical sensitivities (8 replicates) were 320 and 15 pg/ml for the nonconcentrated and concentrated urine samples, respectively.The urine samples were analyzed in both nonconcentrated and 100-fold-concentrated forms. As shown in Fig. 1A and B, the ODs were higher and the dynamic range wider for the 100-fold-concentrated (OD range, 0.132 to 3.060) than for the nonconcentrated (OD range, 0.132 to 0.395) samples. Although a statistically significant difference was reached for patient groups with both the concentration method (P Ͻ 0.001) and the original method (P Ͻ 0.001), practical discrimination between the groups seemed possible ...

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