The Diagnostic Value of Urine Lipoarabinomannan (LAM) Antigen in Childhood Tuberculosis

Abstract

Introduction: Diagnosis of Tuberculosis (TB) in children is difficult because the clinical presentation is not specific, the chest X-ray interpretation has low accuracy and sputum sample is difficult to obtain. Antigen detection test such as rapid urine LAM is a non-invasive alternative for diagnosing TB . Lipoarabinomannan (LAM) is the main component of M.tuberculosis cell wall.

Aim: To determine the diagnostic value of urinary LAM antigen for diagnosis of childhood TB.

Materials and methods: In the present cross-sectional study, subjects were included using consecutive sampling method. All the children aged 0-14 years Suspected of pulmonary or extra pulmonary TB suffering from cough more than two weeks, fever without clear aetiology, loss of body weight or poor weight gain, fatigue, malaise, chronic lymph node enlargement, spine angulation, joint swelling and had history of contact with positive sputum smear adult TB patient were enrolled in the study. Pulmonary and extra pulmonary diagnosis was based on clinical presentation, Tuberculin Skin Test (TST), chest X-ray, Acid Fast Bacillus (AFB) staining and or sputum culture. Urinary LAM level was measured by using Enzyme-Linked Immunosorbent Assay (ELISA). Cut off value and Area Under the Curve (AUC) were determined using ROC statistical analysis (SPSS 21.0). Sensitivity and specificity was measured from 2x2 cross table.

Results: Out of 61 subjects suspected as TB, 49 (80.3%) were eventually diagnosed with TB. Of those diagnosed with TB, 21 (42.9%) were microbiologically confirmed cases either by sputum microscopy (34.7%) or culture (8.2%), whereas 28 subjects were unconfirmed cases (57.1%). The urinary LAM level was higher in subjects with TB (1.80+1.02) mg/l compared to non-TB group (0.46+0.3) mg/l; p<0.001(independent t-test). Urine LAM had 83% sensitivity and 85% specificity with cut off value 0.98 mg/l using microbiological and clinical confirmation as standard reference and 33% sensitivity and 60% specificity with cut off value 1.69 mg/l using microbiological confirmation only.

Conclusion: Urinary LAM has good diagnostic value for childhood TB diagnosis.

Keywords: Biomarker; Serology; Tuberculosis diagnostic research.

[Table/Fig-1]:

Flow chart of the study

[Table/Fig-4]:

ROC curve showed AUC of this test was 0.8 (95%CI 0.64 – 0.96).

[Table/Fig-6]:

Using positivity of microbiology examination as reference standard, ROC curve showed AUC of this test was 0.56 (95% CI 0.41-0.72).