Comparison of 99mTc-DTPA and 51Cr-EDTA for glomerular filtration rate measurement with the continuous infusion method

BACKGROUND

In late 2018, the production of 51Chromium-labelled ethylenediamine tetra-acetic acid (51Cr-EDTA), a validated and widely used radio-isotopic tracer for measuring glomerular filtration rate, was halted. Technetium-99m-diethylenetriaminepentaacetic acid (99mTc-DTPA) has been validated for GFR measurement with a single bolus injection, a procedure not suitable in patients with extracellular compartment hyperhydration. In such cases, a bolus followed by continuous infusion of the tracer is required. The aim of this study was to evaluate whether 99mTc-DTPA with the infusion protocol can replace 51Cr-EDTA for GFR measurement.

METHODS

We conducted a prospective single centre study during February and March 2019. All patients referred for GFR measurement received both radiotracers simultaneously: 51Cr-EDTA and 99mTc-DTPA bolus and continuous infusion were administered concomitantly through the same intravenous route. Over four and a half hours, plasma and urine samples were collected to calculate urinary and plasma clearance.

RESULTS

Twenty-two patients were included (mean age 63.4 ± 17.5 years; 68% men). Mean urinary clearance of 51Cr-EDTA and 99mTc-DTPA was 52.4 ± 22.5 mL/min and 52.8 ± 22.6 mL/min, respectively (p = 0.47), with a mean bias of 0.39 ± 2.50 mL/min, an accuracy within 10% of 100% (95% CI 100; 100) and a Pearson correlation coefficient of 0.994. Mean plasma clearance of 51Cr-EDTA and 99mTc-DTPA was 54.8 ± 20.9 mL/min and 54.4 ± 20.9 mL/min, respectively (p = 0.61), with a mean bias of - 0.43 ± 3.89 mL/min, an accuracy within 10% of 77% (95% CI 59; 91) and a Pearson correlation coefficient of 0.983.

CONCLUSIONS

Urinary and plasma clearance of 99mTc-DTPA can be used with the infusion protocol to measure GFR.

Stability of 25 mg/mL Azacitidine Suspensions Kept in Fridge after Freezing

Azacitidine is supplied as lyophilized powder to be reconstituted with sterile water for injection. The molecule is very unstable in aqueous medium (temperature-dependent process). Advance preparation and leftover management are made difficult by such poor stability. This study evaluates the stability of 25 mg/mL azacitidine suspensions kept for a 1-month period at –20 °C, followed by a 5-day period at 5 °C. Three batches of 7 polypropylene syringes were filled with 2 mL of Vidaza