Comparison of glomerular filtration rates determined using two- and single-blood sample methods with a three-blood sample technique for 2922 paediatric studies.

OBJECTIVE: Several different methods for measuring glomerular filtration rates (GFRs) have been developed in search of a more accurate and simplified technique. Currently, the main methods used are the slope-intercept and distribution volume techniques. In this work, 2922 GFR studies have been retrospectively reanalysed as two- and single-blood sample methods and compared with the three-blood sample data. PATIENTS AND METHODS: Paediatric GFR data from 1/1/1993 to 4/12/2018 using the three-blood sample technique have been reanalysed as two- and single-blood sample methods. The timing of blood sampling was also reviewed.
RESULTS: Both the two- and the single-sample methods provide accurate estimates of GFR in children for all levels of renal function provided that the blood samples are collected at the appropriate times post administration of the tracer. For the highest accuracy, blood for the two-blood samples method should be collected at 2 and 4 h and at 2 h for the single-blood sample method. The relationship between renal clearance and the 2-h volume of distribution (V120) is linear with a line of best fit: GFR (ml/min) = 3.108 × V120 - 2.557.
CONCLUSION: Both the two- and the single-sample techniques can be used to measure GFR in children with the same accuracy as the three-blood sample. With the collection of only a single-blood sample, there are benefits to all involved: patients, families, and nuclear medicine personnel. In addition, institutions have a choice as to which technique to use and for which patients.