To the Editor In the article “The influence of prosthesis diameter in stapes surgery: meta-analysis and systematic review of the literature” reported earlier this year by Laske et al. (1), the authors concluded that in primary stapes surgery, the 0.6-mm prosthesis produces a better hearing outcome when compared with the 0.4-mm prosthesis in absence of tissue interposition or surgical impediments. We would like to thank Laske et al. for addressing this clinically relevant and controversial topic. We have reported earlier on hearing outcome of stapes surgery gathered in the Common Otology Database (COD) (2). This report highlighted the feasibility of the COD as a prospective database, and therefore, we did not report on hearing outcome of all technical differences in stapes surgery. In Table 1, the reader will find the air-bone gap (ABG) closure rates within 10 and 20 dB for the different prosthesis diameters. We have observed a statistically significant difference favoring the 0.5- and 0.6-mm prosthesis. These data can be a useful addition to the cited article.TABLE 1: Prosthesis diameterAlthough we definitely support the idea of a systematic review and subsequent meta-analysis, we think the COD has a clear advantage over a meta-analysis, such as the one performed by Laske et al., for the following reasons. The COD includes all individual thresholds at fixed intervals (preoperative, 3, 6, and 12 months and yearly afterward) in a single database and enables the calculation of a single PTA (0.5-1-2-3 kHz) and the use of postoperative bone conduction (BC) for the measurement of the postoperative air-bone gap (ABG). As reported by De Bruijn et al. (3), the choice of PTA significantly affects postoperative air conduction gain and ABG levels, that is, 4.9 and 4.5 dB, respectively, when comparing a low-frequency PTA with a high-frequency PTA. Additionally, De Bruijn et al. (3) found that the ABG difference between the use of preoperative and postoperative BC to calculate the postoperative ABG ranges between 2.5 and 3.5 dB, depending on which PTA combination is used. In the meta-analysis performed by Laske et al., 2 studies (4,5) used preoperative BC to calculate the postoperative ABG, 1 study (6) used the postoperative BC to calculate the postoperative ABG, whereas another study (7) was unclear on the type of calculation. One study (7) used a PTA of 0.5-1-2-3 kHz, 2 studies (4,5) used a PTA of 0.5-1-2 kHz, and 2 studies (6,8) used a PTA of 0.5-1-2-4 kHz. These factors can potentially act as confounding variables. Laske et al. question the ethics of a prospective randomized controlled trial. We agree on this statement and have to remark that a randomized controlled trial in the field of otology is unreasonable because the rigid inclusion and exclusion criteria would lead to an unrealistic case volume to reach statistical significance. We emphasize the potential of a sustained multicenter high-quality prospective observational database, such as the COD, to meet these sample size needs (2,9). The future of these large-scale observational studies lies in the implementation of a surgical quality management system for each of the contributing centers to minimize selection bias. Vincent Van Rompaey, M.D. Paul Van de Heyning, M.D., Ph.D. Department of Otorhinolaryngology-Head and Neck Surgery Antwerp University Hospital Edegem, Belgium Matthew Yung, M.D., Ph.D. Department of Otolaryngology The Ipswich Hospital NHS Trust Ipswich, Suffolk, U.K.