Impact of using cross-over CV and mean for two different lots of assay control on implementation of Westgard rules in chemical diagnostic tests

• Published in: Practical laboratory medicine 2025-04, Vol.44, p.e00449, Article e00449
• Main Authors: Nabil, Ayman Mohamed, Alsaif, Hayat Mirza, Aljamaan, Muneer Ahmad, Algafly, Abdullah Abdullah H., aleid, Rashad Hassan, Helal, Raji Ali, almutawah, Zainab Ali Hussain, Alzayer, Amani Abdulkareem S., Almutawah, Walaa Ali Hussain, AlKhalaf, Badr Abdullah Motlaq
• Format: Article
• Language: English
• Subjects: Accuracy; Cross-over coefficient; Diagnostic test reliability; Quality control; Reagent lot variation; Westgard rule
• ISSN: 2352-5517; 2352-5517
• DOI: 10.1016/j.plabm.2025.e00449

The main challenges of clinical laboratories concerning quality control include cost-effectiveness, variability in standardized materials, and evolving technologies across various diagnostic fields. While traditional QC practices and automation systems provide for accuracy, gaps exist, especially when applying Westgard rules to control lots for multiple assays. Such gaps result in inconsistent QC outcomes and unaddressed challenges in diagnostic reliability. This study aims to assess the effect of the cross-over coefficient of variation (CV) and mean values for different assay control lots on implementing Westgard rules to improve QC practices and enhance the accuracy and reliability of diagnostic tests in molecular laboratories. Data from 18 Levy-Jennings charts, with two assay control lots, were analyzed. Statistical comparisons of failure rates before and after setting the actual SD were performed using chi-square or T-tests at p