Accuracy and precision of neonatal electronic incubator scales

Measurement of weight in the neonatal intensive care unit demands accuracy and precision. To date, however, no studies exist that independently document the accuracy of infant incubator bed scales. The purpose of this study is to evaluate the Airshields-Vickers Warm Weigh internally mounted incubator bed scale with foam and water mattresses using 500 gm and 1,500 gm standard weights to ascertain the precision of electronic bed scales and to evaluate the differences between nurse weighers. Two experienced neonatal nurses evaluated new incubator bed scales. Each nurse independently collected data and kept the results masked. Eight measurements were obtained from each incubator. Results indicated error beyond +/- 2 gm at 500 gm with the foam mattress and in both weight groups with the water mattress using the Technical Error Measurement (TEM) method. This indicates that the bed scales did not perform within the manufacturer's rated accuracy of +/- 2 gm at the smallest weights found in the clinical area. Weight errors were not judged to be clinically significant by a group of NNP experts.