Evaluation of Sample Rejection Rates in the Biochemistry and Hematology Departments at Parirenyatwa Group of Hospitals: A Retrospective Review from January 2024 to December 2024

Abstract

The efficacy and reliability of clinical laboratory services are foundational to patient safety and appropriate clinical decision-making, necessitating robust Quality Management Systems (QMS). Sample rejection, primarily due to pre-analytical errors, represents a critical failure in the total testing process, leading to delayed diagnoses, increased healthcare costs, and the potential for adverse patient outcomes. This retrospective observational study aimed to comprehensively assess the magnitude and causes of sample rejection at the Parirenyatwa Group of Hospitals (PGH) over a 12-month period (January to December 2024), focusing on the Clinical Chemistry and Hematology departments. The study pursued three specific objectives: to determine the overall rejection rate, identify the most common pre-analytical causes and compare rejection rates between the two major laboratory sections. Utilizing a systematic random sampling procedure for a sample size of N=385 from historical laboratory records, the data were subjected to descriptive analysis to calculate rates and frequencies of error. The results revealed a critically high overall sample rejection rate of 8.0% across both departments, substantially exceeding the international quality benchmark of less than 2% recommended by the World Health Organization. Biochemistry recorded a marginally higher rate (8.3%) compared to Hematology (7.7%). Analysis of rejection reasons confirmed that the problem is overwhelmingly pre-analytical in nature, with the three leading causes being clotted samples (31.1%), hemolyzed samples (21.3%), and insufficient sample volume (18.0%). The majority of rejected specimens originated from inpatient wards. The minimal 0.6% difference in rejection rates between Hematology and Biochemistry is a pivotal finding, suggesting that the root causes are systemic, primarily related to inconsistent phlebotomy techniques, training deficits, and lack of rigorous supervision across the hospital rather than being confined to specific departmental processes. In conclusion, the high and unsustainable sample rejection rate at PGH demands urgent, hospital-wide intervention to safeguard diagnostic quality. Key recommendations include strengthening mandatory phlebotomy training and periodic competency assessments, enhancing quality control and supervision within inpatient wards— the main source of errors—and implementing stricter sample labelling and identification protocols. Addressing these systemic pre-analytical vulnerabilities is essential for improving laboratory efficiency, reducing costs, and ultimately supporting optimal patient management and clinical outcomes.