[Studies of prostate-specific antigen (PSA) immunoassays--differences in characteristic of immunoreactivity and reference materials among the kits].
OBJECTIVE
We conducted this study to examine differences in characteristics of immunoreactivity for free PSA and alpha(1)-antichymotrypsin complex PSA (ACT-PSA) as well as in compositions and concentrations of PSA reference materials among commercially available PSA kits.


METHODS
Fractionated serum samples using a Sephacryl S-200 column were measured by Tandem-R, Delfia-PSA, Ab bead PSA, ACS-PSA, Markit-M and gamma-seminoprotein (gamma-Sm) kits. The calibrators of Tandem-R, Delfia-PSA, Ab bead PSA and Markit-M were fractionated by the same method and measured by Tandem-R. The calibrators of Delfia-PSA, Ab bead PSA and Markit-M and control serums of ACS-PSA were measured by Tandem-R.


RESULTS
Although the characteristic of immunoreactivity of Tandem-R, Delfia-PSA, and Ab bead PSA were found to be similar, they were not shown identical. ACS-PSA was proved to recognize free PSA greater than above three PSA kits, while Markit-M could scarcely detect free PSA. gamma-Sm recognized only free PSA. The calibrators of Tandem-R, Delfia-PSA, Ab bead PSA and Markit-M were proved to be only free PSA. The linear correlation was obtained between Tandem-R and Delfia-PSA or Ab bead PSA or Markit-M. The ratio of Delfia-PSA to Tandem-R, Ab bead PSA to Tandem-R and Markit-M to Tandem-R was 0.66, 0.93 and 2.2, respectively. With regard to relation of ACS-PSA and Tandem-R, two ratios of 0.22 and 0.25 were obtained between the two kits according to the different concentrations of control sera.


CONCLUSIONS
The present studies suggest that the difference in PSA values among the commercial PSA kits results from (1) different characteristics of immunoreactivity for ACT-PSA and free PSA among PSA kits, (2) compositions of PSA calibrators among the kits, and (3) different concentrations of PSA calibrators among the kits.
Umeda
H
H
Dokkyo University School of Medicine.
Sumi
S
S
Honda
M
M
Hosoya
Y
Y
Arai
K
K
Yano
M
M
Koga
F
F
Nakajima
K
K
Nakanishi
K
K
Maeda
S
S
Kitahara
S
S
Yoshida
K
K
D014408:Biomarkers, Tumor / Q000097:blood*; D002138:Calibration; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood*; D011933:Reagent Kits, Diagnostic / Q000592:standards*
D014408:Biomarkers, Tumor; D011933:Reagent Kits, Diagnostic; D017430:Prostate-Specific Antigen