Polyethylene glycol modified LAMP assay enables sensitive and specific clinical detection of varicella-zoster virus

Accurate, timely diagnosis of varicella-zoster virus (VZV) is important for treatment and infection control. While loop-mediated isothermal amplification (LAMP) is operationally simple, nonspecific priming can degrade performance. We assessed a polyethylene glycol-modified LAMP (PEG-LAMP) that tunes the reaction microenvironment via macromolecular crowding. PEG (1 μL per reaction) was titrated across concentrations; 100 mM was selected as the optimized condition because negatives remained at baseline while target amplification kinetics were maintained. PEG-LAMP preserved a log-linear relation between threshold time and input and improved the detection limit from 10³ to 10² copies/μL compared with conventional LAMP. Precision at a fixed input exhibited low variability, and specificity was supported by flat traces in non-target reactions. In a 30-sample panel (15 spiked positives, 15 negatives) tested in parallel by PCR, conventional LAMP, and PEG-LAMP, PEG-LAMP was fully concordant with PCR and yielded shorter time-to-threshold for positives, whereas conventional LAMP produced one false negative and four false positives. Taken together, the results demonstrate that microenvironmental tuning with PEG provides a low-complexity means to suppress nonspecific LAMP while preserving on-target amplification, yielding a lower detection limit and faster time-to-result with PCR-level qualitative agreement in clinical VZV diagnosis.