Retrospective case identification
Based on expected case numbers the last five years is the suggested minimum (2013-present) but as far back as practical to 01/01/2000 would be helpful in evaluating trends more effectively.
1. From RIS/PACS searching for procedure (air enema reduction)
Will under report as procedure not always recorded specifically as air enema
Will under report as cases taken direct to theatre
2. Free text search of radiology reports for “intus*”
Will over report as many studies negative
Will over report incidental small bowel intussusceptions
3. Histopathology free text search for “intus*”
More likely to pick up direct to theatre cases (more likely to have had a resection)
4. Clinical coding for ICD-10 code K56.1 (intussusception)
Least specific but probably most comprehensive search
Does not differentiate type/site of intussusception
Usual coding inaccuracy problems
For the data presented from Sheffield we used 2-4 and cross-referenced the retrieved patient ID numbers. As a minimum, a free text search of radiology reports (2) should pick up the majority of cases from diagnostic and therapeutic imaging.
Even centres that have historically routinely registered cases may need to repeat a search to identify/exclude significant numbers of cases taken directly to theatre (this may be of the order of 5-20% of cases based on the initially available search where ~10% cases were taken directly to theatre).
Case identification is the most labour intensive part of the retrospective review for this condition due to the number of irrelevant cases that the search will produce and the lack of representative clinical codes and accurate coding. This is the reason for the suggested prospective registration of cases from now on even with only limited clinical data collection.