Invited Commentary| Volume 44, ISSUE 3, P260, September 2012

Commentary on ‘No Benefit from Carotid Intervention in Fatal Stroke Prevention for >80 Years Patients’

Open ArchivePublished:July 26, 2012DOI:
      I find the conclusion of this report quite attractive and in line with recent research: invasive treatment of carotid stenosis may not be warranted in most patients >80 years of age with carotid stenosis, especially when female and asymptomatic. However, I am not sure that the data set actually allows this conclusion. We are presented with a 9-year case material of all 80–91-year-old patients analysed retrospectively including two different procedures of which angioplasty was used minimally during the last years. The data set was stratified according to gender and preoperative symptoms.
      Primary end point was perioperative stroke/death, which occurred in 19 cases. A total of 323 patients (270 (84%) men and 53 (16%) women) had 348 procedures (272 in men and 76 in women). This discloses a surprising skewness in the data set: bilateral procedures were performed in 23 women but in only two men. Is this a reflection of female patients being more diseased? The reported higher rate of peripheral vascular disease among female patients supports this impression. Add to this, that the high risk among women in the data set was based on only five incidents. Outcome in several subgroups was compared. Even though outcome was two to three times worse in one group as compared to another, none reached the level of significance. A rough power calculation could have guided the authors: the case material had to be 3–4 times larger to reach statistical significance.
      Secondary end point was 5-year ischaemic stroke/death. Here we are faced with new challenges: median follow-up was only 3 years, and 5-year mortality was calculated alternatively, as only the dead and those observed for at least 5 years were analysed. Out of the total 323 patients, only 160 were included into the long-term outcome calculations: 79 who died within 5 years and 81 alive and observed for 5 years. Thus survival information in 163 patients was disregarded. Consequently, the 5-year all-cause mortality was 49% (79/160), corresponding to a survival rate of 51% – which was substantially lower than the KM calculated 5 years survival of 65%. We are not surprised then, those outcomes based on the limited data set are less favourable than those of the local 80–85-year-old population.
      With these examples, I would like to emphasise the importance of being cautious when subgroup analysis is performed on a limited case material collected over a number of years and analysed retrospectively. Bias is often unavoidable and neither easy to detect nor easy to correct. In addition, bias may be the cause for observed differences credited to clinical parameters.

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