Semi-quantitative immunochromatographic test for prostate specific antigen in whole blood: tossing the coin to predict prostate cancer?
OBJECTIVE
A strip test for the semi-quantitative determination of prostate specific antigen (PSA) based on whole blood was evaluated by the Working Group on Laboratory Diagnostics of the German Urological Association.


METHODS
In 301 men (156 volunteers and 145 referred patients, mean ages 57 years and 64 years) handling and capability of the strip test to predict PSA serum concentrations (Access Hybritech, Beckman Coulter, Inc., Fullerton, CA, USA) relative to a cutoff of 4 micro g/l were investigated. For patients, the strip test was performed by investigators, volunteers accomplished it according to leaflet instructions. Each test result was interpreted by both, the patient/volunteer and an investigator.


RESULTS
24% of the volunteers required assistance with test performance. The overall agreement between Access PSA (range 0.1-29.7) and strip test was 76% (read by participants) and 79% (read by investigators). Within the PSA ranges 0.1-3, 3.1-5 and 5.1-10, participants yielded agreement rates of 89%, 40% and 56%, respectively. Studying the 2.1-10 PSA range most relevant for prostate cancer screening, agreement rate (53%), sensitivity (50%) and specificity (67%) were barely superior to random chance. Volunteers alone (PSA range 0.1-11.3 micro g/l) yielded a specificity of 92%, however, all PSA values above the cutoff (n=8) went unrecognized and all positive strip tests (n=12) were incorrect (sensitivity 0%, positive predictive value 0%).


CONCLUSIONS
Test handling and interpretation was difficult. The rate of false strip test results is disappointing even for PSA ranges remote from the cutoff. In its present form the strip test fails to meet the clinical requirements and its launch to the market was therefore discontinued.
Oberpenning
Frank
F
Department of Urology, University of Münster, Albert-Schweitzer Str. 33, D-48129, Münster, Germany. oberpen@uni-muenster.de
Hetzel
Stefan
S
Weining
Christoph
C
Brandt
Burkhard
B
De Angelis
Gabriela
G
Heinecke
Achim
A
Lein
Michael
M
Fornara
Paolo
P
Schmid
Hans-Peter
HP
Hertle
Lothar
L
Semjonow
Axel
A
D003951:Diagnostic Errors; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity
D011933:Reagent Kits, Diagnostic; D017430:Prostate-Specific Antigen