ITEM 17.  Report time interval from the index tests to the reference standard, and any  treatment administered between them.

 

 

Example

Patients were scheduled to undergo CT colonography prior to conventional colonoscopy, both of which were performed on the same day.[1]
 

In epidemiological terms, studies of diagnostic accuracy are cross-sectional. The results of the index test and reference standard are performed on the same patients at the same time.[2] When delay occurs between doing the index test and the reference standard the condition of the patient may change, leading to worsening or improvement of the target condition or the alternative conditions.

Similar concerns apply if treatment is started after doing the index test but before doing the reference standard.

 

 

References

1.

Yee J, Akerkar GA, Hung RK, Steinauer-Gebauer AM, Wall SD, McQuaid KR. Colorectal neoplasia: performance characteristics of CT colonography for detection in 300 patients. Radiology 2001;219:685-92.
2. Knottnerus JA, Muris JW. Assessment of the accuracy of diagnostic tests: the cross-sectional study. In: Knottnerus JA, ed. The evidence base of clinical diagnosis. London: BMJ Publishing Group, 2002:39-59.