Validity of self-reported Pap smear history in Norwegian women.
OBJECTIVE
To assess the validity of self-reported Papanicolau (Pap) smear history in Norwegian women and to identify characteristics that influence the validity.


METHODS
Interview data from a sample of 16,574 Norwegian women, aged 18-45, in 2004-2005, was compared with information from the population-based cytology register. Crude validity in the self-reports with respect to ever/never having taken a Pap smear was summarized. The validity of the reported interval since last Pap smear was assessed by a smoothed distribution of the reported interval, stratified by the registered interval. Characteristics of influence on validity were identified by logistic regression for true positives (sensitivity and positive predictive value), true negatives (specificity and negative predictive value) and for more than one year discrepancy in time since last Pap smear, between reported and registered interval.


RESULTS
Overall validity was summarized by: concordance = 0.9, sensitivity = 0.97, positive predictive value = 0.92, specificity = 0.55, negative predictive value = 0.78 and report-to-records ratio = 1.51. The variance in the reported interval increased proportionally with the registered interval, and women tended to underestimate the interval (telescoping). Age and registered number of years since last Pap smear had the strongest influence on ever/never and time interval validity, respectively.


CONCLUSIONS
Estimated screening rates, based on self-reporting without organized screening, are biased. Telescoping leads to increased risk for developing invasive disease, because women will postpone their next Pap smear.
Klungsøyr
Ole
O
Department of Screening-based Research, The Cancer Registry of Norway, Montebello, 0310 Oslo, Norway. Ole.Klungsoyr@kreftregisteret.no
Nygård
Mari
M
Skare
Gry
G
Eriksen
Tormod
T
Nygård
Jan F
JF
D000293:Adolescent; D000328:Adult; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D008487:Medical History Taking; D008875:Middle Aged; D009664:Norway; D065006:Papanicolaou Test; D010358:Patient Participation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis*; D014626:Vaginal Smears / Q000379:methods*; D014930:Women