Reproducibility of classification and correction for verification bias as determinants of performance of Papanicolaou smear cytology in the screening setting: experience from the New Independent States of the former Soviet Union cohort study.
OBJECTIVE
To assess impact on interlaboratory agreement of 2 optional modes to convert Papanicolaou classification to Bethesda System (TBS) and demonstrate effect of verification bias correction on test performance in the New Independent States of the former Soviet Union (NIS) cohort study.


METHODS
Conventional Pap smears were classified in NIS laboratories and rescreened in a reference center (RC) using modified Papanicolaou classification. Two optional methods (TBS1, TBS2) were used to convert original classification to TBS. All classifications were tested for interlaboratory agreement and performance indicators with and without verification bias correction.


RESULTS
Interlaboratory agreement of original classification was fair with regular kappa, but substantial with weighted kappa. TBS1 option (Class 2 in atypical squamous cells of undetermined significance [ASCUS]) did not remedy this limited reproducibility. When Class 2+ (borderline dyskaryosis) was used as cutoff for ASCUS (TBS2), interlaboratory agreement was upgraded to moderate and almost perfect. Test performance was significantly different between NIS and RC only for TBS1 option with ASCUS cutoff RC showing better sensitivity/specificity balance by area under receiver operating characteristic curve test.


CONCLUSIONS
In converting traditional classification to TBS, selection of appropriate equivalents to TBS categories has a major impact on interlaboratory agreement and performance indicators.
Syrjänen
Kari
K
Department of Oncology and Radiotherapy, Turku University Hospital, Department of Oral Pathology, University of Turku, Turku, Finland. kari.syrjanen@tyks.fi
Shabalova
Irena
I
Ivanchenko
Olga
O
Kljukina
Ludmila
L
Grunberga
Valerija
V
Syrjänen
Stina
S
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008403:Mass Screening / Q000379:methods* / Q000592:standards; D008875:Middle Aged; D009367:Neoplasm Staging; D015588:Observer Variation; D065006:Papanicolaou Test; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014586:USSR; D002583:Uterine Cervical Neoplasms / Q000145:classification / Q000473:pathology*; D014626:Vaginal Smears / Q000592:standards; D055815:Young Adult; D002578:Uterine Cervical Dysplasia / Q000145:classification / Q000473:pathology*