The Performance of PSA-RIACT in Different Agitation Rate

Received 7/9/2009; revised 7/21/2009; accepted 7/21/2009. For correspondence and reprints contact: Wan-Yu Lin, M.D., Department of Nuclear Medicine, Taichung Veterans General Hospital. 160 Section 3, ChungGung Road, Taichung 407, Taiwan. Tel: (886)4-23741349, Fax: (886)4-23741348, E-mail:[email protected] Background: PSA (prostate specific antigen) is a serine protease of the kallikrein group, found almost exclusively in the prostate. It is a glycoprotein with a molecular weight of 34,000D, which plays a major role in the liquefaction of seminal fluid. According to the standard operative procedure of the PSA-RIACT, agitation with 400 rpm for 2 h is required. However, the number of the shakers that can reach 400 rpm is limited in number in our laboratory. The examination items that require the same instrument should not be operated in the same day. Arranging the examination schedule is not easy in a laboratory since all the following factors should be considered as well: the schedule of the physicians’ out patient clinic, the duration of the examination, the frequency of the examination, the number of the samples per day, the capacity of the radiologist/ technician to handle the examination and the instruments’ capacity. If the different agitation rate plays no role in the results of the radioimmunoassay, it would be much easier to set the schedule of the daily works. Methods: We collected 63 blood samples from male patients arranged to check the PSA level under the physician’s prescription during hospitalization. Informed consents were collected. All the samples were analyzed by an experienced technician in the radioimmunoassay laboratory at Taichung Veterans General Hospital (VGHTC) according to the standard operation procedure of prostate specific antigen (with the agitation rate of 400 rpm) as the controlled group. The examined group was handled according to the standard operation procedure of prostate specific antigen, but with different agitation rate (200 rpm). Pairs of sample were handled by the same technician with the same culture time. The sampling was finished by an automatic pipetting station. The results of the two groups were evaluated by paired student t test and the Pearson’s correlation coefficient. Results: For the 63 included cases, the PSA levels were lower than 4 ng/ml in 38 cases (60%), between 4 ng/ml to 10 ng/ml in 17 cases (27%), between 10 ng/ml to 50 ng/ml in 6 cases (9.5%), and higher than 50 ng/ml in 2 cases (3%). There was good correlation of the paired results in 400 rpm and 200 rpm with the Pearson’s correlation coefficient of 0.99. The results between 400 rpm and 200 rpm were no statistical difference (P = 0.27). Conclusion: Since the results of PSA analysis shows no statistical significance in 400 rpm and 200 rpm, it would be an alternative to incubate the samples in 200 rpm when the 400 rpm-shakers are not available.