Fatores associados a resultados falso-negativos de exames citopatologicos do colo uterino

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Introduction: The spectrum of factors that lead to false-negative (FN) results in cytopathology testing is broad, and dealing with these factors continues to be a challenge. The evaluation of the performance of technologists responsible for testing should be monitored as a way of guaranteeing the quality of results. Objectives: To analyze whether, under routine scrutiny, factors related to the adequacy of the sample, cell pattern and cytomorphological criteria are associated with false-negative results in cytology testing, and to analyze the performance of the cytotechnologists who routinely perform these tests by carrying out a 100% rapid review of negative smears. Methods: This study was carried out at the Cytopathology Laboratory of CAISM/UNICAMP. The smears included in the study were obtained from women who were clients of the National Health Service in Campinas and the surrounding catchment area, undergoing cytology (Papanicolaou smear) as a screening for cervical cancer. To fulfill the objectives of the study, two different methodologies were designed. First, a case-control study was carried out involving 100 smears with a false-negative (FN) result detected by the 100% rapid review system of internal quality control. For each FN result detected, two smears with a true positive (TP) diagnosis made by the same cytotechnologist were identified, and this set of smears formed the control group, making a total sample size of 300 smears. The variables analyzed were established according to the criteria defined by the analysis of adequacy of the sample, cell pattern and cytomorphology. The results were evaluated using bivariate analysis and logistic regression with stepwise variable selection criteria expressed as odds ratios (OR) (95%). The second stage consisted of a cross-sectional study including 62,785 smears classified as negative during routine scrutiny carried out by 24 cytotechnologists. All smears were submitted to the laboratory?s internal quality control using the 100% rapid review method. During this review, the suspect smears were submitted to a detailed review to confirm any alteration and were later reviewed by cytopathologists before a final diagnosis was issued. For the statistical analysis, the cytotechnologists were grouped into tertiles based on the rates of false-negative results, and the rates were compared using the Kruskal-Wallis and Mann-Whitney tests. Results: First study: The number of atypical cells, the appearance of nuclear chromatin, and the distribution and presentation of atypical cells in the smear represented the greatest risk for FN results with odds ratios (OR) of 9.6, 4.2, 4.4 and 3.6, respectively. Inflammatory processes and the presence of blood in the smear also represented a risk for FN results. Second study: A total of 269 false-negative smears were detected, ASC-US and LSIL being the most prevalent diagnoses. For the set of all the diagnoses together, the highest rate of false-negative results attributed to one single cytotechnologist was 8.3 times greater than the lowest rate of false-negative results observed. The cytotechnologists were grouped into tertiles according to the range of false-negative results, which were calculated and analyzed for the set of all the diagnoses together, ASC-US and LSIL. Comparisons between the three ranges and between sets of two were statistically significant for all the diagnoses together, ASC-US and LSIL. Conclusions: First study: Most of the factors associated with FN results are a consequence of the conditions and the techniques used in sample collection, since, in the majority of cases, the lesion may not be adequately represented in the smear. Other confounding factors such as blood and inflammatory processes may also hinder analysis. With respect to cytomorphological alterations, fine chromatin was the characteristic that represented greatest risk for FN results. Second study: The rates of false-negative results vary significantly from one cytotechnologist to another and the most frequent diagnoses in tests with false-negative results were ASC-US and LSIL

ASSUNTO(S)

colo uterino - citopatologia reações falso-negativas controle de qualidade

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