An analysis of serial Minnesota ECG code changes in the London cohort of the WHO Multinational Study of Vascular...

Deterioration and improvement in the electrocardiogram are important outcomes in cardiovascular disease progression assessment. We used a sample of serial records from the WHO Multinational Study of Vascular Disease in Diabetes (WHO MSVDD) to assess Minnesota coding variability.

A constructed subsample of 118 of the 352 paired (baseline and follow-up) and previously Minnesota-coded ECG records from the London cohort was randomised and re-read independently of the first code (respectively 11 and 0.5 years later) by the same two coders. Detailed Minnesota codes were summary coded into groups 1 (CHD unlikely), 2 and 3 (CHD possible and probable, respectively).

Re-reading of the constructed sample for the baseline records (11 years later) generated 21 Summary code reassignments (2 unlikely to possible or probable; 19 possible or probable to unlikely); re-reading for the follow-up records (0.5 years later) generated only 8 summary code reassignments (21 vs 8p < 0.001) (3 unlikely to possible or probable; 4 possible or probable to unlikely; 1 probable to possible). Re-reading increased the estimated net ECG deterioration in the constructed sample from 11.8 % to 25.4%. Consistency analysis showed most variability in marginal baseline abnormalities.

Coding variability is now small though re-reading suggests some time-dependent coding drift. Relative over-reading at baseline suggests that the change reported in the complete WHO MSVDD cohort at follow-up was underestimated and that almost all of the reported ECG deterioration and about half of the reported ECG 'improvement' was real.