To investigate the application value of Six Sigma (6σ) quality management theory and biological variation criteria in the performance evaluation of maternal serological prenatal screening tests during the second trimester.

From January to December 2022, the indoor quality control data of prenatal serological screening for pregnant women during the second trimester at Zhenjiang Maternal and Child Health Care Hospital were collected. The results of external quality assessment (EQA) from National Center for Clinical Laboratories (NCCL) and the EQA data from Jiangsu Prenatal Screening Quality Management System were analyzed. The coefficient of variation (CV) and bias were calculated. The sigma (σ) values of each item were calculated based on the allowable total error (TEa) of the NCCL EQA program and the TEa derived from biological variation. Standardized σ verification charts were plotted, and the quality goal index (QGI) was calculated for items with σ <6. Reasons for the results were analyzed and timely corrections were made.

The σ values of alpha-fetoprotein (AFP) and free β-human chorionic gonadotropin (free β-hCG) under the NCCL standard were all>6, which was the "world-class" level. If the TEa standard is suitable for biological variation, the σ value is more than 6, which is the "world-class" level. Under the optimal TEa standard, the σ value of AFP was 4~5, indicating "good" laboratory performance. At this time, the QGI value<0.8, suggesting that the precision under this standard exceeds the permissible range. Therefore, it is necessary to analyze the influencing factors of this item and prioritize improving the precision.

6σ quality management theory and biological variation specification can be used as a supplement to traditional quality control methods, visually indicating potential adverse factors in the experiment, so as to optimize the quality control scheme and improve the detection efficiency.