Current methods for detecting Mycobacterium tuberculosis (M.tb) in centralized medical facilities are a bottleneck in TB surveillance, particularly in resource-constrained regions. In response, we present a groundbreaking portable bio-tool, the lab-in-a-cartridge (LIC) system, designed for on-site detection of lipoarabinomannan (LAM) in trace amounts within the urine. The innovative design combines pumpless liquid handling and magnetic force-based enrichment with horseradish peroxidase polymer amplification to precisely quantify low biomarker levels. Employing a tetramethylbenzidine-based colorimetric reaction, the LIC enables semi-quantitative LAM detection. This LIC incorporates all necessary reagents, achieving a detection threshold of as low as 0.01 pg/mL in pooled urine samples within 40 minutes. The LIC distinguishes TB patients in clinical urine samples with 92% sensitivity and 88% specificity. This pioneering device not only sets an improved standard for detecting low LAM concentrations but also holds the potential to realize a decentralized diagnosis of TB.