The Diagnostic and Prognostic Value of Urine Lipoarabinomannan in Extrapulmonary Tuberculosis: A Review of Current Evidence
Ankit Kumar1*, Laxmi Devi2 and Surya Kant3
1Assistant Professor, Department of Respiratory Medicine, King George Medical University, Lucknow, Uttar Pradesh, India
2Assistant Professor, Department of Respiratory Medicine, Ganesh Shankar Vidyarthi Medical College, Kanpur
3Professor, Department of Respiratory Medicine, King George's Medical University, Lucknow, UP, India
*Corresponding Author: Ankit Kumar, Assistant Professor, Department of Respiratory Medicine, King George Medical University, Lucknow, Uttar Pradesh, India.
Published: September 14, 2023
DOI: 10.55162/MCMS.05.164
Abstract
Introduction: Tuberculosis (TB) is a global public health problem, with an estimated 10 million new cases and 1.5 million deaths. While pulmonary TB is the most common form of the disease, extrapulmonary TB (EPTB) accounts for 10-20% of all TB cases. EPTB can affect virtually any organ system, with lymph nodes, pleura, and the central nervous system being the most commonly involved sites. The diagnosis of EPTB is often challenging due to the diverse clinical presentations and the limitations of the available diagnostic tools. Delayed diagnosis and treatment of EPTB can result in significant morbidity and mortality. Therefore, there is an urgent need for new and improved diagnostic tools for EPTB.
Lipoarabinomannan: Lipoarabinomannan (LAM) is a glycolipid component of the cell wall of Mycobacterium tuberculosis (MTB), the causative agent of Tuberculosis. LAM is shed by replicating MTB cells and can be detected in various body fluids, including urine, blood, and cerebrospinal fluid (CSF). The detection of LAM in urine has emerged as a promising diagnostic approach for TB, as urine is a readily available and non-invasive specimen that can be easily obtained from patients.
Diagnostic Value of Urine LAM in EPTB: Several studies have evaluated the diagnostic value of urine LAM assays in EPTB, with varying results. A meta-analysis of 18 studies, including 3,383 patients, found that the sensitivity and specificity of urine LAM for the diagnosis of EPTB were 34% and 90%, respectively. However, the sensitivity of urine LAM varied widely depending on the site of EPTB, with the highest sensitivity observed for tuberculous meningitis (TBM) (63%) and the lowest for pericardial TB (5%). The diagnostic accuracy of urine LAM was found to be higher in HIV-positive patients than in HIV-negative patients. In another study, the sensitivity of urine LAM for the diagnosis of TBM was found to be as high as 85%. These findings suggest that urine LAM has a limited but potentially useful role in the diagnosis of EPTB, particularly in settings where other diagnostic tools are unavailable or have limited sensitivity.
Prognostic Value of Urine LAM in EPTB: In addition to its diagnostic value, urine LAM has been shown to have prognostic value in EPTB. Several studies have demonstrated that urine LAM levels are associated with the severity of EPTB and the response to treatment. For example, one study found that urine LAM levels were significantly higher in patients with disseminated TB than in patients with localized TB.