Quality is the heart in management of all laboratories. Due to the good governance concepts, accountability of the whole laboratory process is the main focus of current concern in laboratory medicine. Due to the laboratory quality cycle, reliability cannot be achieved in a clinical laboratory through the control of accuracy in the analytical phase of testing process alone. There should be a certification on the whole laboratory, but not on single analytical process. Precision and accuracy of analyses are not only determined by the analytical procedure but also by preanalytical factors, such as contamination and loss during sampling and sample preparation. Under the broad umbrella of the preanalytical phase can be included requesting test, specimen collection, handling and processing in the process before complete distribution of test samples to multiple work stations [1, 2]. In the total analytical process of clinical specimens, there are many possible preanalytical sources of error .
According to a recent study, mistakes in the preanalytical phase were upto 50 % . Therefore, the application of quality system to laboratory testing requires total quality management in the whole laboratory process, including preanalytical and postanalytical phases. The major aim of the quality system is to reduce or, ideally, eliminate all defects within the whole laboratory process.
ISO 9002:1994 , a quality system in ISO 9000 series, is a model for quality assurance in production, installation, and servicing, which includes a number of clauses providing guidance for the implementation of the quality system. This quality system starts from general quality and documentation plans followed by the internal audit plan step and the launch of the quality system. Finally, the assessment by an external team from an accredited third-party organization and final certification for compliance to ISO 9002 must be performed. The main topics according to ISO 9002 standard include management responsibility, organization, quality system, control of nonconforming product, statistical techniques and etc. Like other manufacturing processes, the clinical laboratory process is a type of service therefore the ISO 9002 can be applied [5, 6]. As the realization of the ISO 9002 standard in the laboratory, all already mentioned topics can also be used . This quality system, which must be maintained and undergo external audit at regular intervals so that certification is confirmed, ensures the product (laboratory analysis service) to clinicians conform regularly to predefined levels of quality .
In Thailand, the ISO 9002:1994 quality system is also implemented for the clinical laboratory. Our laboratory at King Chulalongkorn Memorial Hospital, the largest Thai Red Cross Society hospital, is the first clinical laboratory in Thailand with ISO 9002:1994 certified for the whole unit, including structures, processes and so on. Monitoring of the preanalytical mistakes is one commitment in our quality plan. The aim of this study was to evaluate the types and frequency of mistakes in our laboratory in the preanalytical testing process. We gave the operative definition for a "mistake" as any defect during the entire process, that influenced in any way the quality of the laboratory service.