Estimated T50 calciprotein crystallization test in patients undergoing hemodialysis: Osaka Dialysis Complication Study (ODCS).

BACKGROUND

T50 calciprotein crystallization test (serum calcification propensity, T50) is a blood test which assesses the resistance of the serum to calcification stress in vitro. Because of its limited availability in clinical practice of chronic kidney disease, we aimed to develop equations for estimated T50 (eT50).

METHODS

This was an observational study in 1,651 hemodialysis patients whose T50 was measured by the method Pasch et al. The data sets were divided into two groups for the derivation (N = 1,003) and validation (N = 648) of the equations. Logarithmically transformed values of measured T50 were regressed by relevant variables selected from 36 candidates based on the Akaike's Information Criteria.

RESULTS

Because the initial model A included 19 variables, we developed simpler models B and C with 10 and 5 variables, respectively, for clinical use. All these models included serum phosphate, magnesium, sodium, chloride, and total ion binding capacity. When these equations were validated, the intercept, slope, and R values were 1.130, 0.770, 0.596 for model A, 1.093, 0.782, and 0.597 for model B, and 0.979, 0.806, and 0.573 for model C, respectively. Multivariable-adjusted Fine-Gray analysis showed that a lower eT50 value by model A, B, or model C was an independent predictor of a higher risk of new cardiovascular events in the total cohort as the measured T50 was.

CONCLUSIONS

We developed three equations for eT50 from clinically available variables. These eT50 values may be useful if measured T50 is not available.