Relation between quality of cervical smears and probability of abnormal results.
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Biomedical subjects
Publications and source records attributed to F Buntinx.
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We collected data on 320 patients complaining to their general practitioner of a new episode of chest pain, discomfort or oppression. Relationships were examined between initial signs and symptoms and a follow-up diagnosis after a period of 2 weeks to 2 months. The data were analysed with CART, a statistical decision theory software package. In our first run, the number of misclassifications by CART was 56%. After regrouping of the data and diagnostic categories, there were 37% misclassifications. The most discriminating variable turned out to be pain on palpation. When comparing each of five diagnostic groups to all others, we found a positive predictive value of 27% for gastrointestinal diseases, 72% for cardiovascular disorders, 69% for respiratory diseases, 58% for psychopathology and 73% for chest wall pathology. The CART methodology needs further investigation and testing before any clinical application will be possible in general practice.
Meta-analysis is a way of reviewing literature in a structured and systematic format. A formalized protocol for selection of the reviewed papers and a qualitative as well as quantitative evaluation are essential. Mathematical pooling of the results of the individual studies can be part of the process. A number of pitfalls are possible. However, when performed in a correct way and evaluated critically by the reader, a meta-analysis can add consistently to the medical knowledge concerning a specific subject.
Three different forms of feedback designed to improve the sampling quality of cervical smears were tested in a randomized controlled trial among 179 physicians. The reactions of the doctors to the various interventions are reported as they appeared from their answers in a questionnaire. The influence of the interventions on the employed sampling technique is described on the basis of their answers to a telephone inquiry. The inclusion in laboratory protocols of an evaluation of the sampling quality of the submitted smears was largely appreciated, as was specific advice offered on indication. Monthly overviews comparing the performance of the individual doctor to that of his peers were esteemed by three out of four. Further information, help or training was requested more frequently than average by physicians obtaining inadequately sampled smears relatively often. The number of doctors using the combined spatula and Cytobrush method as sampling technique doubled during the study period.
It is generally accepted that cervical smears are adequately sampled when they contain endocervical and/or metaplastic cells. An extensive literature search via MEDLINE and FAMLI for papers on cervical smears yielded 33 articles providing explicit information both on the country where the study was executed and on the relationship between the adequate sampling of smears and the sampling method used. The correlation between the geographic origin of cervical smears and the proportion of those smears that were adequately sampled was examined. The results were controlled for the sampling method. It was found that the proportion of adequately sampled smears reported in studies in the U.K. is exceedingly low, in contrast with the proportion reported from The Netherlands. The differences between the various countries studied are stable over different sampling methods. It is suggested that, in order to ameliorate the sampling quality of cervical smears, factors associated with the working conditions in particular regions also need be considered.
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Twenty-five general practitioners collected information on 318 contacts of patients with a new episode of chest pain, discomfort or tightness. A list of complaints, signs and symptoms were checked, together with the initial diagnosis, made by the GP immediately after the physical examination. The initial diagnosis was compared to a follow-up diagnosis. The gain in certainty was also compared. The GP made a correct initial diagnosis in 82% of patients. In 8% there was a clinically important difference, and seven of 17 episodes of oesophageal disease were missed. For their initial diagnosis, the GP scored 74% certain, 20% uncertain and no diagnosis in 6%. For the final diagnosis, these figures were 88%, 8% and 4%.
Since the introduction of the Cytobrush for sampling the uterine cervix, some practitioners have ceased taking a concomitant cervical scraping using a spatula. To examine whether Cytobrush sampling alone is adequate for the diagnosis of cervical lesions, the Cytobrush and spatula samples in 444 smears (most with original diagnoses of at least mild dysplasia) were analyzed separately for the presence of diagnostic cells, endocervical cells and squamous cells. Of the 412 smears showing pathologic findings (mild to severe dysplasia or worse), diagnostic cells were present in 400 Cytobrush samples and in 369 spatula samples; the combination of both samples thus gave a 3% gain in correct diagnoses as compared to use of the Cytobrush samples alone. Another 18 smears would have been underdiagnosed based only on the Cytobrush samples. Endocervical cells were present in 95.3% of the Cytobrush samples and 83.8% of the spatula samples; squamous cells were present in 93.9% of the Cytobrush samples and 96.8% of the spatula samples. Analysis confirmed that it is important that the smear should contain both endocervical and squamous cells. A positive relationship between the absence of squamous cells in the Cytobrush sample and the probability of a false-negative assessment was suggested. It thus seems inadvisable to replace the combination sampling method by Cytobrush sampling alone, which may lead to a false-negative diagnosis.