In Response: We thank Dr. Jung for the special interest in our work regarding the tissue and serum levels of tissue inhibitor of metalloproteinase 1 (TIMP-1) as prognostic markers in head and neck squamous cell carcinoma (1).

We have shown in our study that high preoperative serum TIMP-1 levels as well as high expression of TIMP-1 in tumor tissue were linked with poor cause-specific as well as poor relapse-free survival in head and neck squamous cell carcinoma (HNSCC) patients (1). In our study, the median serum level for TIMP-1 immunoreactive protein of HNSCC patients was 527 ng/ml, mean 565 ng/ml. Additionally, the level of the TIMP-1 in 44 healthy controls was lower, median 409 ng/ml, mean 432 ng/ml (P < 0.001). The level of the serum TIMP-1 was very high in the report mentioned by Dr. Jung in his letter and also in previous report by Jung et al. (2). In our study, the TIMP-1 levels in controls equal the plasma levels of ten healthy volunteers in report by Jung (3). In collecting the serum samples, Jung had used serum tubes with additives (kaolin-coated). In our study, the serum samples were all so-called native serum samples, (i.e. collected with tubes with no additives). We also want to point out that in our study all samples were prospective and have been handled in a consistent method.

In conclusion, we appreciate the comments by Dr. Jung and we greatly agree that when estimating the circulating TIMP-1, the interpretation of the results should include a certain reservation, unless the methodological aspects are taken account.

Ruokolainen H, Pääkkö P, Turpeenniemi-Hujanen T. Tissue inhibitor of matrix metalloproteinase-1 is prognostic in head and neck squamous cell carcinoma: comparison of the circulating and tissue immunoreactive protein.
Clin Cancer Res
Jung K, Nowak L, Lein M, et al. What kind of specimen should be selected for determining tissue inhibitor of metalloproteinase_1 (TIMP_1) in blood?
Clin Chim Acta
Jung K. Impact of blood sampling on circulating tissue inhibitors of metalloproteinases. Clin Cancer Res. Letter to the Editor.