LF-LAM TB Antigen vs Xpert MTB/RIF Diagnostic Accuracy in Underweight Suspected Pulmonary TB Patients

Who

• Participants: 52 suspected pulmonary TB patients who were HIV-negative and underweight (BMI <18.5 kg/m²).

• Demographics: 42 males and 10 females; age distribution included 1 (10–19 yrs), 20 (19–43 yrs), 17 (44–60 yrs), and 14 (>60 yrs).

• Sample selection: All were newly suspected pulmonary TB cases able to produce sputum.

• Exclusions: Patients with diabetes, hepatitis, chronic renal failure, malignancy, or HIV.

• Initial enrollment: 70 patients; 52 remained after criteria applied.

What

• Study focus: Evaluation of the LF-LAM TB-Ag urine assay versus Xpert MTB/RIF sputum assay for diagnosing pulmonary TB in underweight, HIV-negative individuals.

• Key findings:

  • LF-LAM TB-Ag sensitivity: 79.59%; specificity: 100% (using Xpert as reference).

  • Significant association between the two tests (chi-square P = 0.002).

  • LF-LAM positivity higher in severely underweight patients (80%) than mildly underweight (68.1%).

  • Xpert positivity similar across underweight categories (93.33% vs. 95.45%).

• Implication: LF-LAM TB-Ag is a potentially useful, simple screening tool for pulmonary TB in severely underweight, HIV-negative patients.

When

• Data collection period: January 2023 – June 2024.

Where

• Setting: Abdul Moeloek Hospital, Lampung Province, Indonesia.

• Location type: Inpatient wards.

Why

• Rationale: To determine whether the LF-LAM TB-Ag urine test—already known as a useful tool in severe TB or HIV-associated TB—can serve as a diagnostic alternative for pulmonary TB in non-HIV, underweight patients, a population at higher risk with limited validated screening tools.

How

• Study design: Observational diagnostic evaluation.

• Procedures:

  • LF-LAM TB-Ag test: Midstream morning urine, tested within 30–60 minutes, using the Alere Determine LAM TB-Ag kit.

  • Xpert MTB/RIF: Morning sputum mixed 2:1 with reagent, shaken 10–15 minutes, then analyzed via GeneXpert cartridge system.

• Analysis: Chi-square test comparing LF-LAM and Xpert results; subgroup analysis by severity of underweight status.

Source: Eksa, D.R., Hendarto, G.S., Sinaga, F.T., Dilangga, P., Herdato, M.J.D., Infianto, A., Ekawati, D., Gozali, A. and Ajipurnomo, A., 2025. Comparative Diagnostic Accuracy of LF-LAM TB Antigen and Xpert MTB/RIF in Pulmonary Tuberculosis among Underweight Patients. Jurnal Respirologi Indonesia, 45(4), pp.272-279.