A comparison of variability in Papanicolaou and liquid-based cytology inadequacy rates using Shewhart control charts |
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Authors: | R. Fox A. B. J. Nix H. Fielder |
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Affiliation: | National Public Health Service for Wales, Temple of Peace and Health, Cardiff, UK. rosemary.fox@nphs.wales.nhs.uk |
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Abstract: | OBJECTIVE: To use Shewhart control charts to compare variability in inadequacy rates from Papanicolaou (Pap) and liquid-based cytology (LBC). DESIGN: Retrospective analysis of quality assurance data. SETTING: Eleven Welsh cytology laboratories. METHODS: Shewhart 'p' charts were plotted for proportions of slides reported as inadequate. Charts were compared for statistical control. MAIN OUTCOME MEASURES: Evidence of statistical control in the processes. RESULTS: Control charts allowed easy interpretation of patterns in the data. Variability in inadequacy rates was much lower for LBC than for Pap cytology. CONCLUSION: Monitoring inadequate rates with Shewhart charts provides more information than tabular monitoring reports, assisting in quality improvement. With respect to inadequacy rates, LBC is less variable than Pap cytology. |
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Keywords: | cervical cytology statistical process control quality assurance performance improvement control chart inadequacy rates liquid-based cytology |
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