Comment and reply on: A randomized crossover trial investigating the ease of use and preference of two dry powder inhalers in patients with asthma of chronic obstructive pulmonary disease.

I read with great interest the article by Job van der Palen et al. [1]. The article describes the comparison of a new single-dose dry powder inhaler, Elpenhaler (EH) (Elpen Pahrmaceutical Co., Inc., Greece) versus the established dry powder inhaler, Accuhaler/Diskus (DK) (GlaxoSmithKline, UK) in patients with chronic obstructive pulmonary disease (COPD) and asthma. The basic conclusion of the authors is as follows: ‘With DK fewer errors were made, more patients preferred DK over EH and patients were more satisfied with DK’. It is the purpose of this letter to demonstrate that this conclusion is misleading since it is based on serious oversights of the design of the study. First, and most importantly, at the time that the study was conducted, EH was not marketed in the Netherlands. It is assumed that ‘instructions of usage’ were translated from English to Dutch (Methods section). It seems that the translation was not accurate as the translation of a unique characteristic and one of the major advantages of the EH device (i.e., visual verification of dose uptake) was omitted. EH allows the patient to visually check after inhalation whether the powder has been inhaled or not. Consequently, the Elpenhaler checklist quoted in Table 1 of the article should have included prior to the last ‘Close inhaler’ step as an additional step for the correct use of the device: After inhalation, check whether all the inhalation powder has been inhaled. Second, in Section 2.2 entitled, ‘Patients’, one reads ‘Patients were 40 years ... were naive to DK and EH for at least 1 year’. It cannot be questioned that the patients were naive to EH; however, it can be questioned whether patients were really naive to DK, since -as stated in Table 2 -disease history ranged between 3 and 13 years. In addition, 72.6% of patients suffered from COPD and fluticasone--salmeterol combination is the drug of choice for this disease. Up to now, besides DK, there is no other combination of those two active ingredients in clinical practice. Doctors and nurses were also naive to EH and not naive to DK; the instructions of medical doctors and nurses to the patients for the correct use of EH relied on the content of the insert and not on their real-life clinical experience with the EH device, compared to DK. The methodology of the study can be questioned since current medical practice for asthma and COPD patients requires the training of the patients before regular use of the inhalation device. The study showed that 110 DK patients (97.3%) and 100 EH patients (88.5%) correctly used the devices after one single instruction (Table 3). The above finding strengthens the position of current medical practice