Drug-induced diseases (DIDs)

Sir,

Apropos of the article on DIDs in a tertiary care teaching hospital in India1, the authors have offered a different context for looking at adverse drug event related data. But, a few points in the article needs clarification. It has been stated that a total of 2381 adverse drug events (ADE) were evaluated and 924 cases of drug induced diseases (DID) were found. But, the criteria for differentiating between the two terms are not clear. Though a definition of both terms has been given, it does not help in identifying the key difference between the two. A clear cut distinction between the two should have been better. Further, the DID rate has been stated to be 38.9 per cent (24 out of 2381) which has been compared with two earlier studies23. But the investigator of these studies have used different denominator for calculation of DID rate which is the number of patients evaluated rather than number of adverse events. Thus, these studies23 are not comparable with the present one1. It is erroneous to calculate DID from number of adverse drug events reported because it may underestimate the rate of DID as one patient may have more than one adverse events or oversestimate as all patients will not have adverse effects.