The impact of the lookback period and definition of confirmatory events on the identification of incident cancer cases in administrative data

Abstract

BackgroundThis cohort study examined the impact of the lengths of lookback and confirmation periods as well as the definition of confirmatory events on the number of incident cancer cases identified and age-standardized cumulative incidences (ACI) estimated in administrative data using German cancer registry data as a benchmark.MethodsACI per 100,000 insured persons for breast, prostate and colorectal cancer were estimated using BARMER Statutory Health Insurance claims data. Incident cancer cases were defined as having an in- or outpatient diagnosis in 2013, no diagnosis in a lookback period of 1 year and a second diagnosis (or death) in a confirmation period of 1 quarter. We varied lookback periods from 1 to 7 years, confirmation periods from 1 to 4 quarters as well as the definition of confirmatory events and compared ACI estimates to cancer registry data.ResultsACI were higher for breast (138.7) and prostate (103.6) but lower for colorectal cancer (42.1) when compared to cancer registries (119.3, 98.0 and 45.5, respectively). Extending the lookback period to 7 years reduced ACI to 129.0, 95.1 and 38.3. An extended confirmation period of 4 quarters increased ACI to 151.3, 114.9 and 46.8. Including breast and colorectal surgeries as a confirmatory event reduced ACI to 114.9 and 37.1, respectively.ConclusionsThe choice of lookback and confirmation periods and the definition of confirmatory events have considerable impact on the number of incident cancer cases identified and ACI estimated. Researchers need to be aware of potential misclassification when identifying incident cancer cases in administrative data. Further validation studies as well as studies using administrative data to estimate cancer incidences should consider several choices of the lookback and confirmation periods and the definition of confirmatory events to show how these parameters impact the validity and robustness of their results.Electronic supplementary materialThe online version of this article (doi:10.1186/s12874-017-0407-4) contains supplementary material, which is available to authorized users.

The effect of the look-back period for estimating incidence using administrative data

“…But with a long look-back period, valuable data is lost for analyses. A short lookback period, on the other hand, carries the risk of misclassifying prevalent and recurrent cases as incident cases [17,18].…”

Validation of an algorithm based on administrative data to detect new onset of atrial fibrillation after cardiac surgery

“…Based on previous studies [29][30][31], three different lookback windows were used to identify previous hospitalizations (i.e., 1, 3 and 6 years) and their impact on accuracy was tested in three distinct algorithms. For each of these lookback windows, we further examined (using distinct algorithms) whether having a concomitant maze procedure (i.e., Table 2 Discharge diagnostic and procedure codes used in the POAF detection algorithms the surgical ablation of chronic AF) at the time of the cardiac surgery of interest influenced accuracy (Table 2).…”

Quality of care in surgical/interventional vascular medicine: what can routinely collected data from the insurance companies achieve?

“…It holds that greater severity of the endpoint is associated with higher validity, while less relevant observations have lower validity (inpatient sensitivity to hypertension 65%, cancer 91% and acute myocardial infarction 94% [44], outpatient sensitivity to back pain 74% and hypertension 81% [19]). Good validity can especially be assumed for mortality-related endpoints among the vascular patient cohort over the age of 65 years [15,16,25,32,38].…”

“…Adequate consideration of the diagnosis-free history (lookback) is recommended for incidence predictions. Czwickla et al were able to show that by taking a lookback period of 7 years, the incidence of cancer is estimated to be about 10% lower (breast cancer 138.7 vs. 129.0 per 100,000 persons, prostate cancer 103.6 vs. 95.1 and colorectal cancer 42.1 vs. 38.3) [16].…”