Self-reported information on the diagnosis of colorectal cancer was reliable but not necessarily valid.
OBJECTIVE
Self-report is commonly used in epidemiologic studies; however, few data exist on the reliability and validity of this method for eliciting information related to the diagnosis of colorectal cancer. We examined the test-retest reliability and validity of colorectal cancer patients reporting on the process of their diagnosis.


METHODS
One hundred and sixteen participants completed two telephone interviews, 1 month apart, and 95 general practitioners (GPs) completed a written questionnaire, to elicit information relating to key elements of the process of diagnosis of colorectal cancer.


RESULTS
Acute symptoms such as rectal bleeding had higher reliability and validity than more general symptoms. Colonoscopy was the most accurately recalled diagnostic test. Recall of diagnosis date, and date of colonoscopy, had high test-retest reliability. There were considerable differences between dates of diagnostic tests given by participants and GPs, but there was no evidence of a bias in a particular direction. Accuracy of recall did not diminish as time from diagnosis increased.


CONCLUSIONS
This study confirms that self-reported symptoms, tests, and dates in the colorectal cancer diagnostic pathway are generally reliable; however, the validity of reported symptoms and tests can be moderate to poor.
Lynch
Brigid M
BM
Viertel Centre for Research in Cancer Control, The Cancer Council Queensland, PO Box 201, Spring Hill 4006, Brisbane, Australia. brigidlynch@qldcancer.com.au
Youlden
Danny
D
Fritschi
Lin
L
Newman
Beth
B
Pakenham
Kenneth I
KI
Leggett
Barbara
B
Owen
Neville
N
Aitken
Joanne F
JF
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000523:psychology; D004812:Epidemiologic Methods; D005194:Family Practice; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000209:etiology; D006801:Humans; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D011594:Psychometrics; D015203:Reproducibility of Results; D012650:Self Disclosure; D013997:Time Factors