CONTENT

The paper by Çalapkulu et al¹ entitled “Evaluation of Whole Blood Viscosity to Predict Stent Restenosis in Patients with Coronary Artery Disease” was read with great interest, and the authors are congratulated. However, there are some comments about the article.

In their retrospective case-control study, the authors evaluated the relationship between whole blood viscosity (WBV) and in-stent restenosis (ISR) in patients with prior coronary stent implantation. They wrote that they measured the high-shear rate viscosity (208 sec⁻¹) (HSR) and low-shear rate viscosity (0.5 sec⁻¹) (LSR) using De Simone et al² formula. However, they used formula for HRT (208 sec⁻¹) = (0.12 × HCT (%)) + 0.17 (total protein (g/L) − 2.07) and for LSR (0.5 sec⁻¹) = (1.89 × HCT (%)) + 3.76 (total protein (g/L) − 78.42), which is different from the original formula of De Simone et al.²

The original and validated with viscometer formulas are:²

HRT (208 sec⁻¹) = 0.12 × HCT (%) + 0.17 × total plasma protein (g/dL) − 2.07

LSR (0.5 sec⁻¹) = 1.89 × HCT (%) + 3.76 total plasma protein (g/dL) − 78.42.

The formula is valid only throughout the range of hematocrit (32%-53%) and plasma protein concentrations (5.4-9.5 g/100 mL).² According to the original formula, the range of HSR (208 sec⁻¹) was 2.7-5.9 cP, and the range of LSR (0.5 sec⁻¹) was 2.4-57.5 cP. However, in the Çalapkulu et al¹ study the HSR value was 16.8 ± 1.0 cP in the ISR group and 15.6 ± 0.9 cP in the control group, and the LSR value was 83.1 ± 8.4 cP in the ISR group and 80.8 ± 8.0 cP in the control group. These results were out of the original formula’s calculated HSR and LSR ranges.

In the literature, several different formulas^3-7 were used in the calculation of HSR and LSR values; however, the only validated formula with a viscometer was De Simone et al² formula. So, the formula discrepancy could affect the study results.

In conclusion, the study results may check with the original formula. The comparison will show whether there is a differences in the results of the different formulas or not. This comparison will contribute to the literature on whether the formula discrepancy affects the results or not.

Footnotes

Declaration of Interests: The author have no conflicts of interest to declare.

References

1. Çalapkulu Y, Erdoğan M, Aslan AN. Evaluation of whole blood viscosity to predict stent restenosis in patients with coronary artery disease. Anatol J Cardiol. 2025;29(9):503-511.
2. De Simone G, Devereux RB, Chien S, Alderman MH, Atlas SA, Laragh JH. Relation of blood viscosity to demographic and physiologic variables and to cardiovascular risk factors in apparently normal adults. Circulation. 1990;81(1):107-117.
3. Nwose EU, Richards RS. Whole blood viscosity extrapolation formula: note on appropriateness of units. N Am J Med Sci. 2011;3(8):384-386.
4. Tamariz LJ, Young JH, Pankow JS. Blood viscosity and hematocrit as risk factors for type 2 diabetes mellitus: the atherosclerosis risk in communities (ARIC) study. Am J Epidemiol. 2008;168(10):1153-1160.
5. Vosseler M, Beutel A, Schäfer S. Parameters of blood viscosity do not correlate with the extent of coronary and carotid atherosclerosis and with endothelial function in patients undergoing coronary angiography. Clin Hemorheol Microcirc. 2012;52(2-4):245-254.
6. De Simone G, Devereux RB, Chinali M. Association of blood pressure with blood viscosity in American Indians: the Strong Heart Study. Hypertension. 2005;45(4):625-630.
7. Wong ML, Dong C, Esposito K. Elevated stress-hemoconcentration in major depression is normalized by antidepressant treatment: secondary analysis from a randomized, double-blind clinical trial and relevance to cardiovascular disease risk. PLoS One. 2008;3(7):e2350-.