List of studies excluded from the review.

<div><p>Background</p><p>Lean methodology, originally developed in the manufacturing sector, is a process management philosophy focused on maximizing value by eliminating waste. Its application in laboratory settings, particularly concerning laboratory turnaround times (TAT), involves a systematic approach to identifying inefficiencies and optimizing processes to enhance value for end customers.</p><p>Methods</p><p>This systematic review was registered in PROSPERO with identification number (CRD42024552350) and reported based on the 2020 PRISMA checklist. An extensive search strategy was performed using PubMed, Scopus, and Embase databases and gray literatures. Advanced searching was used using Boolean operators (AND & OR). After articles were exported to endnote x8, duplications were removed and articles were selected based on titles, abstracts, and full texts. The illegibility of the articles was independently assessed by the three authors (NC, DMB, and BBT), and the disagreements were settled through scientific consensus. Methodological quality was assessed using JBI critical appraisal checklist.</p><p>Discussion</p><p>In this review, electronic databases search yielded 1261 articles, of which 7 met the inclusion criteria. The review demonstrated, implementation of lean principle into the routine laboratory testing had an overall impact 76.1% on reducing laboratory TAT. Transportation, manual data processing, inefficient workflow, and the heavy workload were identified as the main wasteful procedures. To eliminate these non-value-added steps, several intervention techniques were implemented, including the use of a barcoding system, process redesign, workflow optimization, hiring additional staff, and relocating the sample collection room closer to the result distribution center. Lean implementation is crucial in the medical laboratory industry for optimizing processes, reducing TAT, and ultimately enhancing customer satisfaction. As a result, all clinical laboratories should adopt and implement lean principles in their routine testing processes. The medical laboratory industry should also proactively look for and apply lean tools, provide ongoing training, and foster awareness among laboratory staffs.</p></div>