Harrison Wayne N, Teale Alison M J, Jones Suzanne P, Mohammed Mohammed A
Department of Public Health and Epidemiology, University of Birmingham, Birmingham, UK.
BMC Public Health. 2007 Aug 1;7:191. doi: 10.1186/1471-2458-7-191.
Historically there has been a wide variation in the proportion of inadequate smears between general practices. Cervical screening in the UK is undergoing a fundamental change by moving from conventional to liquid based cytology (LBC). The main driver for this change has been a predicted reduction in the proportions of inadequate samples. This study investigates the effect of LBC on the variation in the proportion of inadequate samples between general practices using Shewhart's theory of variation and control charts.
Routinely collected cervical cytology data was obtained for all general practices in two localities in South Staffordshire for periods before and after the introduction of liquid based cytology. Control charts of the proportion of inadequate smears were plotted for the practices stratified by laboratory. A standardised measure of variation for all of the practices in each laboratory and each time period was also calculated.
Following the introduction of liquid based cytology the overall proportion of inadequate samples in the two localities fell from 11.8 to 1.3% (p < 0.05). This fall was associated with a reduction in the average variation between the GP practices in the two localities from 1.6 to 1.0 standard deviations. There has also been a reduction in the number of practices showing special cause variation from eight to one following the introduction of liquid based cytology.
A reduction in the proportion of inadequate samples has been realised in these localities. The reduction in the overall proportion of inadequate samples has also been accompanied by a reduction in variation between GP practices.
从历史上看，不同全科医疗诊所涂片不合格比例差异很大。英国的宫颈筛查正经历从传统细胞学检查向液基细胞学检查（LBC）的根本性转变。这一转变的主要推动因素是预计不合格样本比例会降低。本研究运用休哈特变异理论和控制图，调查液基细胞学检查对不同全科医疗诊所之间不合格样本比例差异的影响。
获取了南斯塔福德郡两个地区所有全科医疗诊所在引入液基细胞学检查前后各时间段的常规宫颈细胞学数据。针对按实验室分层的诊所绘制了不合格涂片比例的控制图。还计算了每个实验室和每个时间段内所有诊所变异的标准化度量值。
引入液基细胞学检查后，两个地区不合格样本的总体比例从11.8%降至1.3%（p < 0.05）。这一下降与两个地区全科医疗诊所之间平均变异从1.6个标准差降至1.0个标准差相关。引入液基细胞学检查后，显示特殊原因变异的诊所数量也从8家减少到1家。
这些地区实现了不合格样本比例的降低。不合格样本总体比例的降低还伴随着全科医疗诊所之间变异的减少。
