Pre-analytical Factors Influencing Blood Sample Rejection Rate in the Hematology Laboratory of the Philippine General Hospital from 2018 to 2022: A Cross-sectional Study.

Background and objective: Blood collection errors are one of the most common causes of laboratory sample rejection in the pre-analytical phase of the testing process. This study aims to determine the frequency and identify the pre-analytical factors that lead to rejection of samples meant for the hematology laboratory.

Methods: This cross-sectional, retrospective study analyzed blood samples received and rejected by the Hematology Division of the University of the Philippines - Philippine General Hospital from 2018 to 2022. Data were extracted from the Division's annual reports and sample rejection logbooks. The causes and frequency of sample rejections, as well as the hospital locations of the patients involved were presented using frequency tables.

Results: Out of 1,072,366 blood samples received during the study period, 61,935 (5.78%) were rejected. The most common cause of rejection was clotted blood samples for both routine hematology (86.31%) and coagulation (44.43%). Clotted samples were the predominant cause of sample rejection across most age groups, with the exception of the neonatal and infancy groups, where inadequate sample quantity was the primary issue. The highest rejection rate was seen in the emergency department (65.71%) and intensive care units (9.68%).

Conclusion: The rejection rate in our institution was higher than reported in previous global studies. The main causes of rejection were identified as clotted blood samples and inadequate blood volume for routine hematology and coagulation testing. Notably, the highest rejection rates for hematology-related requests occurred in critical areas, including the emergency department, intensive care units, and obstetrics and gynecology.