Evaluation on the Stability of Pooled Sera for External Quality Assessment of Tumor Marker Assays / 임상검사와정도관리

BACKGROUND: Specimens for the external quality assessment (EQA) need to be highly stable during the EQA process. Therefore, we evaluated the stability of pooled sera (PS) for tumor markers including alpha fetoprotein (AFP), carcinoembryonic antigen (CEA), carbohydrate antigen 125 (CA 125), and carbohydrate antigen 19-9 (CA 19-9). METHODS: PS with 2 different levels (high and low) of each of the 4 tumor markers were collected and stored at -20degrees C, 4degrees C, and room temperature (RT). The concentration of each tumor marker was then measured after storage under these different conditions at baseline and on days 1, 3, 7, 14, 30, 90, and 181. Internal quality control (QC) results during the evaluation period were also analyzed. RESULTS: Irrespective of storage conditions, coefficients of variation (CVs) of AFP and CA 125 levels in the PS during the evaluation period ranged from 3.3% to 7.5% in EQA assays and were similar to the CVs of QC assays. However, the levels of CEA detected in PS stored at -20degrees C, and 4degrees C, showed higher variability, with CVs ranging from 4.0% to 10.4%, and samples stored at RT showed especially high CVs, i.e., >8.3%. Samples for CA 19-9 testing stored at RT also showed lower stability than the QC samples as well as samples stored at -20degrees C, after 3 days. CONCLUSIONS: CEA and CA 19-9 levels in PS showed higher variability than AFP and CA 125, especially when stored at RT. These results indicate that all EQA specimens for tumor marker assays need to be tested as soon as possible and not stored at RT for longer than 3 days during the EQA process.

p53 Mutation in Gastric Carcinoma Detected by PCR - SSCP and Direct - Sequencing / 대한암학회지

PURPOSE: p53 gene mutations, one of the most common alterations found in human tumors, has also been detected in gastric carcinoma, and shown to have a crucial and early role in gastric carcinogenesis of intestinal type and mainly associated with tumor progression in the cancer of diffuse type. We tried to investigate the frequency of p53 mutations in 27 gastric carcinomas. MATERIALS AND METHODS: Fresh tumor tissue from a series of gastric carcinoma was screened for p53 mutations by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) with silver staining and confirmed by direct-sequencing in 27 cases of gastric carcinoma. Immunohistochemical method for p53 protein accumulation was also performed in the same cases. RESULTS: Immunohistochemistry revealed 20 of 27 cases of gastric carcinoma, positive for p53. PCR-SSCP analysis of p53 exons 5-8 detected mobility shift in 4 out of 20 p53-positive tumors; three from exon 5 and the other from exon 7, respectively. DNA sequencing of exon 5 showed CGC to CAC point mutation in one of three cases; exon 7, ATC to AAC point mutation. It seemed that there was no correlation between genetic alterations of p53 gene detected by PCR-SSCP and expression of p53 protein by immunohistochemistry. CONCLUSIOAS: Our results suggest that mutations of the p53 gene are rare genetic events in carcinogenesis of gastric carcinomas. There was discrepancy between mutations screened by PCR-SSCP and overexpressions in immunohistochemical staining.