Retrospective evaluation of gynecologic cytodiagnosis. II. Interlaboratory reproducibility as shown in rescreening large consecutive samples of reported cases.

Two laboratories exchanged and rescreened a large sample of cases with cervicovaginal smears they had consecutively accessioned to examine the reproducibility of gynecologic cytodiagnosis under optimum conditions. At least a "working agreement" (diagnoses within +/- 1 category on a ten-category scale) was achieved in diagnoses of normal, benign reaction and squamous abnormality (from minimal dysplasia though invasive cancer) in 18,859 cases (96.8%), of endometrial abnormality in 21 cases (42%) and of "unsatisfactory" in 99 cases (20.7%). Larger differences occurred in greater than or equal to 30% of cases except in the categories of "normal" and "benign reaction," reaching a maximum of 82% for moderate dysplasia. Reexamining 382 cases decreased disagreement by category to the 20% to 65% range only in the five categories of dysplasia plus carcinoma in situ. Agreement was not predicated on the presence of endocervical cells or squamous metaplasia; the basis for "unsatisfactory" calls was not uniform. Comparison of the laboratories' diagnoses with referee diagnoses or, on 178 cases, with tissue diagnoses also demonstrated differences in diagnostic criteria.

Measuring screening skills in gynecologic cytology. Results of voluntary self-assessment.

When the Clinical Laboratory Improvement Act (CLIA) was passed in 1967, the Centers for Disease Control (CDC) became interested in evaluating screening performance in cytodiagnosis. Finding no validated performance measurement methods that could be used on a national scale, the CDC initiated a program of sequential investigations to develop information that would describe the state of the art in microscopic performance in gynecologic cytopathology. The first of these experiments developed a method, the Self-Assessment Workshop, to measure performance at the microscope by using sets of glass slides. This paper describes the method, its validation process and participant performance over a 15-year period. Study results indicated that cytotechnologists and pathologists tended to correctly identify specimens (slides) in the negative and benign reaction categories in up to 95% of responses, but on slides of dysplasia they made 12% of their calls too low. Carcinomas in situ and invasive squamous cancers were undercalled in only about 5% of responses, but endometrial adenocarcinomas and other rare malignancies were undercalled in as much as 20%. The self-assessment technique is a practical, useful tool for identifying cytology personnel with serious deficiencies in cell location/identification skills and is well accepted by cytotechnologists and pathologists. However its limitations should be kept in mind: screening results from this simulated test should not be extrapolated to routine work performance; the screening time limit of five minutes per slide may adversely affect performance; and, finally, these results may reflect state-of-the-art performance only in voluntary, not mandatory, settings.

Laboratory reliability of the Papanicolaou smear.

Variation in clinical cytology diagnoses was examined at the microscope and in the cytology laboratory as a unit. Results provide preliminary information about the comparability of cytologic diagnosis under specified conditions. In onsite proficiency testing using "normed" smears with a wide range of findings, 814 individual cytotechnologists and cytopathologists from 306 laboratories in 44 states made the target diagnosis in 63.8% of 8929 cases. False negative diagnoses were made in 7.5% of 4520 smears with moderate dysplasia through frank malignancy, and false positive diagnoses were recorded in 8.9% of 3808 smears with no more than benign atypia. Evaluation of a sample of actual work output from two laboratories showed 3.2 to 3.4% false positive and 4.8 to 11.2% false negative diagnoses on the cases rescreened.

Effects of reducing DDT usage on total DDT storage in humans.

Agricultural uses of the insecticide DDT were cancelled by the U.S. Environmental Protection Agency December 31, 1972. However, the domestic use of DDT had begun to decline before this action. Beginning July 1969, residues of DDT and its metabolites were measured in human adipose tissue collected through an annual national survey. Levels of total DDT equivalent residues in human adipose have decreased slightly, but the frequencies of finding DDT or its metabolites have remained high. The most marked decline in residue concentration has been found in the youngest age group (0-14 years). Approximately 80 percent of the total DDT equivalent found in this survey was DDE. These data show that the reduction of the agricultural uses of DDT has decreased human exposure to and storage of this chemical.

Racial stratification of organochlorine insecticide residues in human adipose tissue.

The racial stratification of residues of total DDT equivalent, heptachlor epoxide, oxychlordane, dieldrin, beta-benzene hexachloride and lindane in human adipose tissue was studied. Samples of human adipose tissue were obtained from locations selected in the contiguous United States according to a stratified, proportionate-random survey design and chemically analyzed for selected organochlorine pesticides. The most marked case of racial difference in residue level was total DDT equivalent. Samples from Negros contained almost twice as much of this chemical as did samples from Caucasians. Racial stratification also was found in the frequency of lindane. Lindane was detected about twice as often in samples from Negros than in samples from Caucasians. Little racial differences were noted for residues of beta-benzene hexachloride, heptachlor epoxide, dieldrin and oxychlordane.