The Clinical Validation of a Dried Blood Spot Method for Simultaneous Tacrolimus and Creatinine Measurement

M. I. Francke¹, S. Bouarfa², B. van Domburg², D. van de Velde², M. E. Hellemons³, O. C. Manintveld⁴, S. M. Last-Koopmans⁵, M. B. Mulder², D. A. Hesselink¹, B. C. de Winter²

¹Internal medicine, nephrology and transplantation, Erasmus MC, University Medical Center, Rotterdam, Netherlands, ²Hospital Pharmacy, Erasmus MC, University Medical Center, Rotterdam, Netherlands, ³Pulmonary medicine, Erasmus MC, University Medical Center, Rotterdam, Netherlands, ⁴Cardiology, Erasmus MC, University Medical Center, Rotterdam, Netherlands, ⁵Hematology, Erasmus MC, University Medical Center, Rotterdam, Netherlands

Meeting: 2021 American Transplant Congress

Abstract number: 275

Keywords: Immunosuppression, Methodology, Monitoring

Topic: Clinical Science » Kidney » Kidney Immunosuppression: Novel Regimens and Drug Minimization

Session Information

Session Name: Kidney Immunosuppression

Session Type: Rapid Fire Oral Abstract

Date: Monday, June 7, 2021

Session Time: 6:00pm-7:00pm

Presentation Time: 6:10pm-6:15pm

Location: Virtual

*Purpose: Monitoring tacrolimus concentrations and kidney function after transplantation is important to avoid tacrolimus under- and overexposure and its clinical consequences, including acute nephrotoxicity. Using dried blood spot (DBS) instead of a venipuncture for blood sampling has several advantages: it allows blood sampling at home and it makes it easier to draw blood samples at a specific or at multiple time points (e.g. for an AUC measurement).

*Methods: In this study, a DBS sampling method for tacrolimus and creatinine concentration measurement in blood was clinically validated, by comparing pre-dose whole-blood and serum concentrations (for tacrolimus and creatinine, respectively) obtained by a venipuncture to concentrations measured via DBS. The need for a DBS correction factor and hematocrit correction using near infrared spectroscopy was evaluated. Deming regression was used for validation and potential bias was evaluated with a Bland-Altman analysis.

*Results: A total of 50 solid organ transplant recipients was included in the analysis. We calculated the following conversion formula for tacrolimus: [Tacrolimus]_DBS+1.49)/1.788, with a Deming intercept of 0.272 (95%-CI -0.53 to 1.08) and a slope of 0.960 (95%-CI 0.84 to 1.07). Using this conversion formula, 92% of the tacrolimus measurements were within the 20% limits of agreement (LOA) and 76% of the tacrolimus measurements were within the 15% LOA (Figure 1). We calculated the following conversion formula for creatinine: [Creatinine]_DBS+0.8069)/0.9077, with a Deming intercept of -0.5261 (95%-CI -12.73 to 11.68) and a slope of 1.004 (95% CI 0.92 to 1.08), respectively. Using this conversion formula, 94% of the creatinine measurements were within the 15% LOA. For both tacrolimus and creatinine, no additional correction for hematocrit was required.

*Conclusions: DBS sampling was clinically validated and can be used in clinical practice for simultaneous measurement of tacrolimus and creatinine with the use of a conversion formula. An additional correction for hematocrit was not required.

To cite this abstract in AMA style:

Francke MI, Bouarfa S, Domburg Bvan, Velde Dvande, Hellemons ME, Manintveld OC, Last-Koopmans SM, Mulder MB, Hesselink DA, Winter BCde. The Clinical Validation of a Dried Blood Spot Method for Simultaneous Tacrolimus and Creatinine Measurement [abstract]. Am J Transplant. 2021; 21 (suppl 3). https://atcmeetingabstracts.com/abstract/the-clinical-validation-of-a-dried-blood-spot-method-for-simultaneous-tacrolimus-and-creatinine-measurement/. Accessed May 17, 2025.

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