Abstract
The detection of lipoarabinomannan (LAM) antigens in body fluids has several potential advantages compared with the diagnostic methods used currently. The aim of this study was to evaluate the possible role of the detection of LAM in the serum and the urine as a diagnostic aid in the diagnosis of different forms of tuberculosis (TB). This study included 62 newly confirmed tuberculosis cases classified into two groups: group A included patients with pulmonary TB (n=36), and was further divided into two groups: group A1 [the smear-positive pulmonary TB group (n=24)] and group A2 [the smearnegative pulmonary TB group (n=12)]; group B included the extrapulmonary TB group (n=26); and 10 apparently healthy individuals served as the control group. The LAM level was measured in the serum and the urine by an enzyme-linked immunosorbant assay. The mean level of quantitative serum LAM was higher in group A1 (0.55±0.20?ng/ml) compared with group A2 (0.44±0.30?ng/ml) or group B (0.41±0.27?ng/ml). The mean level of quantitative urine LAM was higher in group A1 (0.81±0.24?ng/ml) compared with group B (0.72±0.35?ng/ml) and group A2 (0.65±0.37?ng/ml; P<0.001). The quantitative urine LAM test correlated positively with the degree of bacillary burden (P<0.05). Quantitative serum LAM had a sensitivity of 88.7%, specificity 90%, accuracy 88.9%, positive predictive value 98.2%, and negative predictive value 56.3%. Quantitative urine LAM had a sensitivity of 85.5%, specificity 90%, accuracy 86.1%, positive predictive value 98.1%, and negative predictive value 50%. A combination of serum and urine LAM tests identified that 98.4% of the cases with a positive TB culture correlated with higher serum LAM levels. Advanced chest radiography involvement and TB culture correlated with higher urine LAM levels (P<0.05). The LAM test is a valuable addition in the diagnosis of TB and its different forms. A combination of quantitative serum and urine LAM increased the sensitivity of the test. The quantitative urine LAM test offers additional clinical insight into the degree of TB disease severity and has more applicability.
Highlights
Tuberculosis (TB) ranks alongside HIV as a leading cause of death worldwide
The mean level of quantitative serum LAM was higher in group A1 (0.55±0.20?ng/ml) compared with group A2 (0.44±0.30?ng/ml) or group B (0.41±0.27?ng/ml)
Quantitative serum LAM had a sensitivity of 88.7%, specificity 90%, accuracy 88.9%, positive predictive value 98.2%, and negative predictive value
Summary
Metabolically active or degrading bacterial cells during TB infection; the detection of LAM antigens in body fluids has several potential advantages compared with the diagnostic tests used currently [3]. Qualitative LAM-ELISA (Chemogen Inc., Portland, Oregon, USA) was the first LAM targeting the assayed prototype [5,6,7,8,9]. Later, another commercial version named Clearview TB ELISA (Alere Inc., formerly Inverness Medical Innovations Inc., Waltham, Massachusetts, USA) was launched [10,11]. The detection of lipoarabinomannan (LAM) antigens in body fluids has several potential advantages compared with the diagnostic methods used currently
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