Performance of 3 methods for quality control for gynecologic cytology diagnoses.

OBJECTIVE: To evaluate performance and viability of internal quality control (QC) strategies in a public health laboratory of the state of São Paulo. STUDY DESIGN: A retrospective study was performed with 3 QC strategies to improve internal cytologic diagnoses: morphologic guided-list criteria (MGLC), 100% rapid-rescreening (100% RR) of negative slides ("turret" method) and 10% rescreening (10% R) of negative slides. Cases were examined at Adolfo Lutz Institute, São Paulo, Brazil, from 2002 to 2004. Histopathologic results, when available, were considered gold standard; cytologic consensus diagnosis was by 2 pathologists when histologic results were unavailable. RESULTS: MGLC selected 20.7% samples with cytologic atypias, 10% R selected 0.6% and RR selected 2.5%. Cytologic/histologic initial concordance was 57.4%, low-grade squamous intra-epithelial lesion false negative rate was 34.9% and high-grade squamous intraepithelial lesion false negative rate was 12.2%. After diagnosis, consensus concordance was 97.2%. CONCLUSION: The 100% RR and 10% R QC strategies detected more false negative cases in liquid-based cytology than in conventional Pap smears. The 100% RR strategy reduced the false negative results and allowed evaluation of individual staff performance. The 10% R strategy did not offer significant results. We concluded that association of MGLC and 100% RR strategies might improve cytologic diagnostic quality.

100% rapid rescreening for quality assurance in a quality control program in a public health cytologic laboratory.

OBJECTIVE: To verij5 the efficacy of the quality control (QC) program in a cytologic laboratwy with a rapid rescreening (RR) protocol. STUDY DESIGN: RR, according to the Turret RR method, of all samples initially screened as negative at the Laboratory of Cytology, Adolfo Lutz Institute, was performed. The slides were reviewed for 60 seconds. Suspect smears were fully checked by 2 reviewers to determine the final diagnoses. A total of 2954 sequential cytologic results were considered in this study. Of the 2954, 2568 (86.9%) were considered initially negative according to our internal QC, and these cases underwent RR. Also, 10% were randomly selected from these negative cases for full reviewing. The internal QC in our laboratory includes review of cases selected according to clinical and cytomorphologic criteria. RESULTS: Among the 2954 total cases, QC detected 386 (13%) atypias with final diagnoses reported according to The Bethesda System 2001 as follows: 82 (2.18%) low grade squamous intraepithelial lesions (LSILs), 35 (1.18%) high grade squamous intraepithelial lesions (HSILs), 2 (0.06%) squamous cell carcinomas, 105 (3.5%) atypical cells of undetermined significance (ASC-US), 4 (0.12%) atypical endocervical cells (AECs) and 158 (5.3%) unsatisfactory samples. RR of 2568 smears initially considered negative selected 194 (7.5%) slides. Of the 194, 146 (75.3%) were negative, 28 (14.4%) ASC-US, 5 (2.6%) AEC, 1 (0.5%) LSIL and 14 (7.2%) unsatisfactory. Full review of a 10% random fraction of the 2568 cases interpreted as negative did not detect lesions but did detect 5 (1.95%) unsatisfactory samples. CONCLUSION: Internal QC used in our laboratory based on clinical and cytomorphologic criteria to select cases for review proved to be an efficient method of detecting HSIL and cervical cancer. The consensus basis of this program strongly limits the false positive and false negative rates and also provides subjects with continuing education. One hundred percent RR is more efficient than 10% full reviewing in detecting cervical abnormalities.