Objective To evaluate the role of substrate depletion limit parameters（enzyme linearity extension function） in BS-2000M2 automatic chemistry analysis system.Methods High-level samples were determined parallelly by decreased volume parameters（dilution） and substrate depletion limit parameters（enzyme linearity extension function）. A total of 10 common kinetic chemistry items were involved,including alanine aminotransferase（ALT）,aspartate aminotransferase（AST）,alkaline phosphatase（ALP）,gamma-glutamyltransferase（GGT）,lactate dehydrogenase（LDH）,alpha-hydroxybutyrate dehydrogenase（α-HBDH）,creatine kinase（CK）,creatine kinase MB isoenzyme（CK-MB）,alpha-amylase（α-AMY） and urea. The relative biases between enzyme linearity extension function and dilution were calculated. The main wavelength absorbance（A） at the end point of reaction range was recorded to determine whether substrate depletion occurred. The effectiveness of parameters was evaluated by comparing manual calculation results with actual reaction curve or result flags. Results According to the criteria of WS/T403—2012 or allowable total error（TEa） from the National Center for Clinical Laboratories' external quality assessment,the reportable ranges' upper limits of ALT,AST,ALP,GGT,LDH,α-HBDH,CK,CK-MB,α-AMY and urea were extended to 3 339 U/L,7 411 U/L,3 407 U/L,3 945 U/L,7 646 U/L,9 783 U/L,14 106 U/L,3 296 U/L,9 700 U/L and 54 mmol/L,respectively. The manual calculation results were consistent with actual reaction curve or result flags,and no false positive or negative substrate depletion was observed. According to the sample level distribution of ALT,AST,ALP,GGT,LDH,α-HBDH,CK,CK-MB,α-AMY and urea,100.00%,100.00%,100.00%,100.00%,100.00%,100.00%,99.96%,100.00%,100.00% and 99.97% of samples can be obtained final results through a single assay,when enzyme linearity extension function was employed. No error result occurred in all samples.Conclusions The enzyme linearity extension function in BS-2000M2 can effectively solve the risk of false negative results for high-level samples,reduce rerun frequency and shorten sample turn-around time.
