New BNMS guidelines for measurement of glomerular filtration rate: To adopt or not?

Abstract

The British Nuclear Medicine Society (BNMS) has recently published new guidelines for the measurement of glomerular filtration rate (GFR). The new guidelines recommend replacing the “slope-intercept” (SI) method, which involves taking multiple blood samples, with a “single sample” (SS) method. The time that the single blood sample is withdrawn from the patient is chosen based on estimates of the patient’s GFR, or the most recent GFR measurement where one is available. Whilst the single sample method would be less invasive for patients and entail less work for staff (sampling, counting etc.) there is a perception that single sample methods are generally less accurate and precise compared to multiple sample methods. By applying the new method to historical data from our facility we hope to verify that measurement of a single sample withdrawn at a carefully chosen time can yield results that are as valid as those obtained using the SI method. A retrospective study is carried out by applying the new method proposed by BNMS to data obtained from approximately 100 GFR studies undertaken at our facility over the past two years. The optimum sampling time is determined for each patient and a GFR based on the single sample method is calculated and compared to the value originally calculated based on the SI method.