Aim: The aim of the study was to evaluate the sample rejections reasons by the quality indicators and six sigma process, to determine the acceptability of the rejection reasons and to improve them during the follow-up process.

Material and Method: The data were obtained from the laboratory information management system (LIS). The rejection reasons were grouped according to IFCC harmonization of the quality indicators severity level 1. Pareto analysis was done. The defects per million opportunities (DPMO) and six sigma levels were calculated.

Results: The total sample rejection rate was 0.346% in the central laboratory and 1.083% in the emergency laboratory. Rejection reasons were; Hemolysis Sample, Clotted Sample, Incorrect Fill Level in the hospital, Hemolysis Sample, Clotted Samples in the Emergency Department, Hemolysis Sample, Incorrect Fill Level, Other in outpatients clinic, Hemolysis Sample, Clotted Sample, Incorrect Filling Level in inpatients clinic respectively. Sigma value for "Hemolysis sample"; inpatients, outpatient clinics, emergency room and the entire hospital were 4.6; 4.4; 4.1; 4.5 respectively and for the clotted sample Sigma value were 4.9; 4.5; 4.2; 4.7 respectively. The sigma value of all the other rejection causes were determined as >4.6.

Conclusion: In thıs study, the frequency of sample rejection on the basis of hospital and department (inpatient, outpatient, emergency) was found to be acceptable. To increase the current quality by increasing the Sigma values; we think that clinical and cause based analysis of error rates should be done regularly.