Internal quality control (IQC) for routine and specialist hemostasis testing represents a mandatory requirement for assays offered by clinical laboratories under International Organization for Standardization, Code of Federal Regulations, and Clinical and Laboratory Standards Institute standards. The underlying principle is that regular IQC audits the analytical performance of automated, semiautomated, and manual methods. This review investigates IQC practices, including benefits, limitations, frequency per time period or batch, sources of material used, primary supplier, third party or in-house, plus troubleshooting when IQC falls outside acceptance criteria. To assess IQC practice, the UK National External Quality Assessment Scheme (NEQAS) Blood Coagulation distributed a questionnaire to 1,200 participants enrolled in our scheme that collected details of the local practices for IQC testing. We received returns from 127 centers that described their local practices for the frequency of IQC, the type of IQC material employed, acceptance criteria for IQC data, and troubleshooting protocols for IQC failures. The data collected as part of an NEQAS BC questionnaire confirmed that all the participants returning answers to the questionnaire meet the standards for regular IQC testing for the hemostasis assays they perform.
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