This is the largest study to date of patients examining the relationship between anti-thyroid drugs (ATDs) and bone marrow suppression in the form of agranulocytosis and pancytopenia. The study estimated the incidence of these complications in patients on ATDs at 0.3% for agranulocytosis and 0.01% for pancytopenia. This is in keeping with the previous literature. The onset of these complications was at any point during treatment course however the cumulative incidence plateaued at 100 days post initiation. The study failed to determine any statistically significant risk factors and this is in keeping with the consensus that these the immunological mechanisms involved cannot be predicted by background factors. 100% of patients in the agranulocytosis group (n=50) were successfully treated with currently available treatments (including GCSF, steroids and supportive therapy). 80% of patients who developed pancytopenia (n=5) had prior agranulocytosis. And in this group one patient died.

 

• This is an excellent paper representing the largest study to date and hence contains information useful to our daily clinical practice.
• Clinicians should remain vigilant throughout for these adverse reactions as they can occur at any moment in the treatment course.
• In this study there were 4 patients with agranulocytosis who were not symptomatic, purely being picked up by routine FBC. However the paper does not detail their clinical course (except that they all were treated successfully) and this represents a 0.0001% of patients on ATDs. Hence it is difficult to advocate routine FBC monitoring.
• Reassuringly currently available treatments were successful in treating all patients with agranulocytosis.
• The study could have looked at daily/cumulative ATD doses as a risk factor for developing bone marrow suppression.
• It would have been useful if the paper had detailed the management of their hyperthyroidism after the development of bone marrow suppression.