Worldwide, the urgent need for more sensitive rapid lateral flow tests (LFTs) for early disease diagnosis is driving advances in quantum technologies. Spin-enhanced nanodiamond LFTs offer the potential for a sensitivity step change, yet to date only model systems have been studied with few clinical samples. Herein, we report the largest spin-enhanced LFT clinical evaluation, focusing on SARS-CoV-2 antigen as an exemplar. The limit of detection for recombinant antigens was 0.67 pg/ml, and inactivated whole virus wild-type and Omicron variants were 13 TCID 50 /mL and 8.8 TCID 50 /mL, respectively. Our blinded clinical study with 103 patient upper respiratory tract swab samples showed 95.1% sensitivity (Ct ≤ 30) and 100% specificity benchmarked to RT-qPCR, with no cross-reactivity to influenza A, RSV, and Rhinovirus. Analysis of trial data indicates spin-enhanced LFTs could diagnose SARS-CoV-2 on average 2.0 days earlier than conventional gold nanoparticle LFTs with identical antibodies, and just 0.6 days after RT-qPCR. Quantum-enhanced LFT sensitivity would have detected ~69,400 more patients in a single day at the peak of Omicron, reducing the transmission risk and protecting populations. Our findings mark an important milestone in the emerging field of quantum-enhanced diagnostics, with the potential for significant health-economic benefits to patients, populations, health systems and society.