The Clinical Use Of Sarcosine

Prostate cancer as the most common male malignant tumor, with a high rate of morbidity and mortality, and its diagnosis has been a problem plagued many clinicians. At present the main diagnostic marker for laboratory diagnosis of prostate cancer is prostate specific antigen, but its diagnostic sensitivity and specificity are difficult to meet the clinical request. Sarcosine as newly discovered diagnostic marker in the early diagnosis of prostatic cancer, its role has received extensive attention. Objective To establish the new sarcosine detection method, to evaluate the performance of the new method, to study the sarcosine in prostate cancer diagnosis value. Methods1. To use sarcosine oxidase detection method and enzymatic method for creatinine detection method as the foundation, by experimenting with different concentrations of reactants and detection parameters, to set different reagents for the detection the low concentration sarcosine samples, the optimal results of reagent concentration and parameters combination is the new measuring method.2. According to CLSI documents, through the precision experiment, detection limit experiment, linear experiment, recovery test and reference interval experiments, to evaluation sarcosine oxidase method to detect urine sarcosine level.3. To Collect70clinical samples, including health group in27cases;19cases of patients with benign prostate hyperplasia; prostate cancer patients in24cases, all samples have been detected creatine, sarcosine and prostate specific antigen and free prostate specific antigen, the detection results for statistical analysis, to assess the sarcosine in prostate cancer diagnosis application value.4. Removal samples of the patients with benign prostatic hyperplasia and prostate cancer in the prostate specific antigen results≥20ng/ml, including18cases of patients with benign prostatic hyperplasia and prostate cancer in18patients, of these samples on the corresponding detection results for statistical analysis, to assess sarcosine in prostate cancer diagnosis application value with prostate specific antigen<20ng/ml. Results The target concentration were2.0umol/L sarcosine solution and2.9umol/L fresh urine specimen test results show that, the total Imprecision<14%; the5.0umol/L and10.0umol/L sarcosine solution and6.35umol/L and9.8umol/L fresh urine specimen test results show that the total Imprecision<10%. The blank limit (LoB) is about0.35umol/L; detection limit (LoD) when the sample is sarcosine solution=1.10umol/L, fresh urine specimen=1.18umol/L; Quantitative limit (LoQ) for sarcosine solution=1.90umol/L, urine specimen=2.05umol/L. Sarcosine concentration in the2.05-125.65umol/L range, the test results is linear. Recovery test results show that the quantity of added sarcosine is2-20umol/L, the recovery test results is65.3%-90.5%. Clinical sample determination results show that healthy crowd urine sarcosine level of reference interal0.01umol/g creatinine -0.06umol/g creatinine, urine sarcosine level without the effects of age and gender. No matter how the results of prostate specific antigen, prostatic hyperplasia and prostate cancer group creatine/creatinine ratio the results showed statistical significance. When does not distinguish between prostate specific antigen results, creatine/creatinine ratio results in differential diagnosis of benign prostate hyperplasia and prostate cancer in the area under the ROC curve of AUC=0.774(95%confidence interval0.625-0.926), to sarcosine/creatinine ratio of0.06umol/g creatinine as the cutoff value, differential diagnosis of the73.7%specificity and91.7%sensitivity. When the results of the prostate-specific antigen<20ng/ml, sarcosine/creatinine ratio results in the differential diagnosis of benign prostatic hyperplasia and prostate cancer under the ROC curve area AUC=0.799(95%confidence interval,0.644-0.955) to sarcosine/creatinine ratio of0.06umol/g creatinine as the cutoff value, differential diagnosis of the72.2%specificity and94.4%sensitivity. Conclusion The results of this study show that sarcosine oxidase method detecting urine sarcosine level, its precision、the detection limit and the linear range can meet the requirements of clinical laboratory, but still need improve the calibrator matrix in order to improve the detection accuracy. Sarcosine can be as independent diagnostic marker for prostate cancer, especially when the differential diagnosis of benign prostatic hyperplasia and prostate cancer diagnostic efficacy is superior to the prostate-specific antigen.