The research group at University College London introduced the concept of standardizing the quantification of risk by assessing risk of sudden death or equivalent malignant arrhythmia event occurring during the subsequent 5 years of follow-up after diagnosis. While the aims in the recent article by Norrish et al.1 published in this journal are laudable, it is imperative to highlight the methodological shortcomings underlying their analysis. The authors aim to assess the ability of the electrocardiogram (ECG) risk-score and other aspects of the 12-lead ECG to predict ‘major arrhythmic cardiac event’. They selected a subset (356/1029) of the multi-centre cohort of paediatric patients with hypertrophic cardiomyopathy (HCM) used to construct the HCM Risk-Kids algorithm, where ECGs had been archived. This subset however consisted mainly of recently recruited patients, and so median follow-up was only 3.9 years (interquartile range Q1–Q3 2.0–7.7).1 A major concern is that Norrish et al. did not restrict their analysis to include only those survivors who had reached 5 years of follow-up (n = 77 + 68 = 145), and the patients who had a ‘major arrhythmic cardiac event’ within 5 years of follow-up (n = 17). Instead they compared all patients without events, even if 25% of them had <2 years follow-up, with all patients who had major arrhythmic cardiac event, even if 8 of them had an event later than 5 years of follow-up. Thus, in fact, only 17 (patients with major arrhythmic cardiac event within 5 years) + 145 (patients with ≥5 years follow-up without event) = 162 of the patients are actually statistically informative about the end-point of major arrhythmic cardiac event within 5 years.1 This constitutes only 46% of the total ECG group analysed. The other 194 actually confuse the results as patients with high-risk ECG features and short follow-up might have had a major arrhythmic cardiac event later on within the 5-year span. Similarly, the ECGs of patients with major arrhythmic cardiac event after >5 years of follow-up might have evolved more ECG changes closer to the event as shown in other studies.2 Thus including these late major arrhythmic cardiac events will underestimate the sensitivity of the method.