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Assessment of tumour markers on the Maglumi 2000 Chemiluminescence Immunoassay System

Tumour markers have been widely used in clinical settings for early cancer detection, diagnosis, prognosis and recurrence surveillance. Due to the growing usage, it is of vital importance to assess the performance of common tumour markers on in-vitro diagnosis instruments. In this study, the most commonly used tumour markers have been selected to evaluate the performance of the SNIBE Maglumi 2000  chemiluminescence immunoassay system by comparing with our reference methods.

by Dr Xiao Hu, Dr Sheng Kang, Zhiyun Duan and Professor Guichen Zhang

Tumour markers are substances that rise abnormally in the body when cancer is present. They are useful indicators for cancer risk determination, screening, diagnosis, prognosis, post-treatment surveillance and recurrence monitoring [1]. Alpha-fetoprotein (AFP) is a well established marker in liver cancer diagnosis and post-treatment monitoring [2]. Another well studied tumour marker, prostate-specific antigen (PSA), is recommended for the screening of prostate cancer with men over 50 years old [3]. Carcinoembryonic antigen (CEA) is particularly used as a tumour marker for bowel cancer. It measures the response to treatment and monitors whether the disease has revisited [4]. Elevated serum ferritin has been found in patients with pancreatic cancer, breast cancer, colon cancer, non small cell lung cancer, hepatocellular carcinoma and Hodgkin’s lymphoma [5]. Cancer antigen 125 (CA 125) is a marker commonly used for following up patients with ovarian cancer after treatment [6], while cancer antigen 15-3 (CA 15-3) is widely used for breast cancer management [7]. Cancer antigen 19-9 (CA 19-9) is the best validated marker for pancreatic cancer post-treatment evaluation [8]. Cytokeratin 19 fragment (CYFRA 21-1) and squamous cell carcinoma antigen (SCCA) are useful markers for lung cancer diagnosis in combination with other markers [9] [10]. This study has evaluated the performance of ten tumour markers on the SNIBE Maglumi 2000 chemiluminescence immunoassay system.

According to the principle and method of the CLSI EP5-A2 guideline [11], we made some adjustments to evaluate the precision of ten tumour markers. Intra-assay precision was evaluated on three different levels of serum samples. Each sample was repeatedly measured for 20 times in the same run to calculate the coefficient of variation (CV%). Inter-assay precision was assessed by repeatedly measuring three different levels of samples for 10 days with the same batch of kit. Samples were run in duplicates, two runs per day with at least 3 hours time interval to calculate the coefficient of variation. The results are displayed as mean value and CV%. Table 1 lists the precision results of ten tumour markers. The CVs of the intra- and inter-assays were less than 4.12% and 6.67% respectively (Table 1).

Method comparison
Serum samples from patients with benign diseases to various cancers were offered by the clinical laboratory of our hospital. The patient names were coded with confidentiality. The samples were measured by our reference system and the SNIBE Maglumi 2000 system to form correlation dot plots. Concordance between SNIBE Maglumi 2000 and reference systems for each tumour marker was analysed. For each tested marker, the number of serum samples is ranged from 166 to 460.

By comparing with our reference methods, good correlations were shown between the SNIBE Maglumi 2000 and the ROCHE Cobas e601 or the ABBOTT Architect i2000. The slopes for all markers were between 0.853 and 1.361 while the intercepts ranges from -2.515 to +5.138 (Figure 1A-J). Total PSA has the highest correlation between the SNIBE Maglumi 2000 and the ROCHE Cobas e601 while the lowest relevance (R2=0.981) was seen in CA 19-9 between the SNIBE Maglumi 2000 and the ROCHE Cobas e601 (Figure 1). The total coincidence rate is between 93.7% (Figure 1I) and 99.6% (Figure 1B).

In this study, we have evaluated the performance of the SNIBE Maglumi 2000 chemiluminescence immunoassay system via ten tumour markers. The intra-assay precision and inter-assay precision for all markers examined here are highly acceptable. By comparing with our reference methods, a high correlation has been shown for all markers tested with the SNIBE Maglumi 2000 system. The total coincidence rate is within the acceptable range for all markers examined. To conclude, the SNIBE Maglumi 2000 system is reliable for the measurement of tumour markers in clinical use.

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The authors
Xiao Hu* MD, Sheng Kang PhD, Zhiyun Duan MSc, Dept of Clinical Laboratory, Shenzhen Sixth People’s Hospital, Shenzhen, Guangdong 518052, China
Guichen Zhang Professor, PhD, MD, Medical College, Shenzhen University, Shenzhen, Guangdong 518052 China
(*Corresponding author:  xiao121386@163.com)