The diagnostic accuracy of urine-based tests for bladder cancer varies greatly by patient.
BACKGROUND
Spectrum effects refer to the phenomenon that test performance varies across subgroups of a population. When spectrum effects occur during diagnostic testing for cancer, difficult patient misdiagnoses can occur. Our objective was to evaluate the effect of test indication, age, gender, race, and smoking status on the performance characteristics of two commonly used diagnostic tests for bladder cancer, urine cytology and fluorescence in situ hybridization (FISH).


METHODS
We assessed all subjects who underwent cystoscopy, cytology, and FISH at our institution from 2003 to 2012. The standard diagnostic test performance metrics were calculated using marginal models to account for clustered/repeated measures within subjects. We calculated test performance for the overall cohort by test indication as well as by key patient variables: age, gender, race, and smoking status.


RESULTS
A total of 4023 cystoscopy-cytology pairs and 1696 FISH-cystoscopy pairs were included in the analysis. In both FISH and cytology, increasing age, male gender, and history of smoking were associated with increased sensitivity and decreased specificity. FISH performance was most impacted by age, with an increase in sensitivity from 17 % at age 40 to 49 % at age 80. The same was true of cytology, with an increase in sensitivity from 50 % at age 40 to 67 % at age 80. Sensitivity of FISH was higher for a previous diagnosis of bladder cancer (46 %) than for hematuria (26 %). Test indication had no impact on the performance of cytology and race had no significant impact on the performance of either test.


CONCLUSIONS
The diagnostic performance of urine cytology and FISH vary significantly according to the patient demographic in which they were tested. Hence, the reporting of spectrum effects in diagnostic tests should become part of standard practice. Patient-related factors must contextualize the clinicians' interpretation of test results and their decision-making.
Division of Urology, Duke University Medical Center, Durham, NC, 27710, USA.
Ajay
A
Gopalakrishna
Division of Urology, Duke University Medical Center, Durham, NC, 27710, USA.
Thomas A
TA
Longo
Division of Urology, Duke University Medical Center, Durham, NC, 27710, USA.
Joseph J
JJ
Fantony
Department of Urology, University of California San Diego, San Diego, CA, USA.
Richmond
R
Owusu
Department of Pathology, Duke University Medical Center, Durham, NC, USA.
Wen-Chi
WC
Foo
Department of Pathology, Duke University Medical Center, Durham, NC, USA.
Rajesh
R
Dash
Division of Urology, Duke University Medical Center, Durham, NC, 27710, USA. brant.inman@duke.edu.
Brant A
BA
Inman
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003558:Cystoscopy / Q000639:trends; D005260:Female; D006417:Hematuria / Q000175:diagnosis / Q000652:urine; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D016482:Urinalysis / Q000592:standards*; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis* / Q000601:surgery / Q000652:urine*
Bladder cancer; Cytology; FISH; Sensitivity; Specificity; Spectrum effects