Hou et al. have performed a challenging audit of monitoring for myelosuppression in US Veterans within the first weeks after immunomodulator initiation for inflammatory bowel disease (IBD). Based on the least stringent interpretation of published practical guidelines, the authors report a low rate of myelosuppression monitoring, with a huge variability (0–83%) among facilities.
There is an emerging evidence for a poor implementation of practical guidelines in the field of IBD management.[2-4] Potential reasons for that failure could be related to the physicians, the patients and various socio-economic factors, including the modalities of the local health systems. However, the degree of personal conscience and conviction of individual physicians and hospital teams may be regarded as crucial. This is indirectly suggested here because of the huge variability in guideline implementation among facilities. In another study on colonoscopic surveillance in IBD restricted to homogenous referral university centres, the implementation rate ranged from 27% to 70% among physicians. It is likely that nonconvinced physicians do not properly inform and motivate their patients, which can result in turn in poor adherence to the tests, if prescribed.
Another important point is to determine whether poor implementation of guidelines has deleterious medical consequences that can be considered as the ultimate justification of guideline relevance. For instance, we were able in a colonoscopic surveillance study nested in the CESAME cohort to demonstrate that cancers that were diagnosed in nonsurveyed patients were more advanced than those detected in patients properly monitored.
In the study of Hou et al., it is likely than most of the patients were exposed to thiopurines without previous testing for TMPT. Given the established incidence of myelosuppression in such a context,[5, 6] about 30 patients should have developed severe neutropenia, often with clinical consequences leading to white blood cell test! We are frustrated not to have these data. It has been suggested that only a close (weekly) monitoring is able to detect early severe neutropenias and to stop drugs with the possibility to limit myelosuppression worsening. Even in this ideal context, I am not sure that neutropenia detection and drug stopping always alter the evolution of myelosuppression, with its potential severe clinical consequences (including death). This would be hard, if not impossible, to demonstrate through a dedicated study. In the Veteran population study, about 20 patients could have been diagnosed with total TPMT deficiency before thiopurine initiation. Prohibiting thiopurine prescription in such patients is for me the best prevention for early severe myelosuppression.