In Familial Mediterranean Fever, soluble TREM-1 plasma level is higher in case of amyloidosis.

Dear Editor

We read with interest the article by Dr Gorlier et al. in which they aimed to evaluate the soluble form of triggering receptor expressed on myeloid cells-1 (sTREM-1) activation in Familial Mediterranean Fever (FMF).[1] They reached the conclusion that sTREM-1 plasma levels can be more specific to FMF patients with amyloidosis. We have certain points to make in order to understand the conclusions that can be drawn related to the molecule.

First, there is research in the literature on diseases of the adaptive immune system, especially on systemic lupus erythematosus and systemic sclerosis where sTREM-1 was found to be correlated with disease activity.[2-4] You also shared the study on septic conditions.[5] We are curious about the opinion of the authors on the status of this potential marker among a variety of conditions. Perhaps a new study comparing these different conditions would enhance our understanding.

Second, there appear to be two potential biases related to this study. When comparing the FMF groups with and without amyloidosis, the significant difference in age should be highlighted. In the FMF with amyloidosis group, the mean age was 60.2 ± 16.3 yr, whereas in the FMF without amyloidosis group, the mean age was 40.9 ± 11.2 (P < 10–4). Another bias is related to kidney function. There are studies where sTREM-1 is increased in kidney injury.[6] The probability of sTREM-1 signalling kidney damage rather than amyloid deposition should not be overlooked, as this lowers the specificity of the molecule. For example, a potential study comparing FMF-related amyloidosis patients with high and normal creatinine levels could show us the actual specificity of sTREM-1 to amyloidosis.

It would be of interest to hear the opinion of the authors on these points and to have studies on this matter with higher statistical power and with control groups.