Colonoscopic factors associated with adenoma detection in a national colorectal cancer screening program.

BACKGROUND AND STUDY AIMS: Adenoma detection is a key objective of colonoscopy, particularly in the context of colorectal cancer screening. The aim of this observational study was to identify the technical colonoscopy factors associated with adenoma detection. PATIENTS AND METHODS: The study analyzed data from the English Bowel Cancer Screening Programme. The indication for all colonoscopies was a positive fecal occult blood test. The relationships between the following colonoscopy factors and adenoma detection (one or more adenomas, advanced adenomas, right-sided adenomas, and total number of adenomas) were examined in multivariable analyses: bowel preparation quality, cecal intubation, withdrawal time, rectal retroversion, colonoscopist experience, antispasmodic use, sedation use, and start time of procedure. The following patient factors were controlled for: age, sex, body mass index, smoking, alcohol, deprivation, and geographical location. RESULTS: A total of 31088 colonoscopies were analyzed. The following technical factors increased the relative risk of adenoma detection (P < 0.001 in multivariable analysis unless otherwise stated): cecal intubation, increased withdrawal time, higher quality bowel preparation, intravenous antispasmodic use, earlier procedure start time within a session (P = 0.018), and greater colonoscopist experience. Detection of advanced and right-sided adenomas also increased with these factors. Adenoma detection did not differ between sedated and unsedated colonoscopy (P = 0.143). CONCLUSION: This study demonstrated important associations between colonoscopy practice and adenoma detection. Use of intravenous antispasmodic was associated with increased adenoma detection. The effect of the start time of colonoscopy suggests that endoscopist fatigue may have a deleterious impact on adenoma detection.

A practical application of analysing weighted kappa for panels of experts and EQA schemes in pathology.

BACKGROUND: Kappa statistics are frequently used to analyse observer agreement for panels of experts and External Quality Assurance (EQA) schemes and generally treat all disagreements as total disagreement. However, the differences between ordered categories may not be of equal importance (eg, the difference between grades 1 vs 2 compared with 1 vs 3). Weighted kappa can be used to adjust for this when comparing a small number of readers, but this has not as yet been applied to the large number of readers typical of a national EQA scheme. AIM: To develop and validate a method for applying weighted kappa to a large number of readers within the context of a real dataset: the UK National Urological Pathology EQA Scheme for prostatic biopsies. METHODS: Data on Gleason grade recorded by 19 expert readers were extracted from the fixed text responses of 20 cancer cases from four circulations of the EQA scheme. Composite kappa, currently used to compute an unweighted kappa for large numbers of readers, was compared with the mean kappa for all pairwise combinations of readers. Weighted kappa generalised for multiple readers was compared with the newly developed 'pairwise-weighted' kappa. RESULTS: For unweighted analyses, the median increase from composite to pairwise kappa was 0.006 (range -0.005 to +0.052). The difference between the pairwise-weighted kappa and generalised weighted kappa for multiple readers never exceeded ±0.01. CONCLUSION: Pairwise-weighted kappa is a suitable and highly accurate approximation to weighted kappa for multiple readers.

Measuring interobserver variation in a pathology EQA scheme using weighted κ for multiple readers.

BACKGROUND: A Urological Pathology External Quality Assurance (EQA) Scheme in the UK has reported observer variation in the diagnosis and grading of adenocarcinoma in prostatic biopsies using basic κ statistics, which rate all disagreements equally. AIM: The aim of this study is to use customised weighting schemes to report κ statistics that reflect the closeness of interobserver agreement in the prostate EQA scheme. METHODS: A total of 83, 114 and 116 pathologists took part, respectively, in three web-based circulations and were classified as either expert or other readers. For analyses of diagnosis, there were 10, 8 and 8 cases in the three circulations, respectively. For analyses of Gleason Sum Score, only invasive cases were included, leaving 5, 5 and 6 cases, respectively. Analyses were conducted using customised weighting schemes with 'pairwise-weighted' κ for multiple readers. RESULTS: Analysis of diagnosis for all circulations and all readers gave a composite κ value of 0.86 and pairwise-weighted κ (κ(p-w)) value of 0.91, both regarded as 'almost perfect' agreement. This was due to the high proportion of responses that showed partial agreement. Analysis of Gleason Sum Score gave κ=0.38 and κ(p-w)=0.58 over all circulations and all readers, indicating that discrepancies occur at the boundary between adjacent grades and may not be as clinically significant as suggested by composite κ. CONCLUSION: Weighted κ show higher levels of agreement than previously reported as they have the advantage of applying weighting, which reflects the relative importance of different types of discordance in diagnosis or grading. Agreement on grading remained low.