Hi Sebastián Castro-Trujillo, Bland-Altman plots are commonly used to assess the agreement between two measurement methods. They can provide valuable insights into the level of agreement and any potential biases between the methods being compared. Considering your situation, it's important to interpret the Bland-Altman plots accurately. If you observe a skew in the plots, it suggests a systematic difference between your in-house method and the commercial ELISA kits. This discrepancy could be due to the different approaches used in determining positive or negative results.

To address the reviewers' concerns, you can explain the fundamental differences in measurement values and highlight that the commercial ELISA kits utilize arbitrary values for classification, while your in-house method uses absolute optical density. This distinction could contribute to the observed differences in the Bland-Altman plots and to further support your argument, you could consider conducting additional analyses, such as comparing the performance of the different methods using other statistical measures like sensitivity, specificity, or diagnostic accuracy. This would provide a more comprehensive evaluation of the diagnostic test and help you present a well-rounded analysis to the reviewers.