[Precision and accuracy of body weight assessment in hospitalized adults]

Body weight (BW) is widely used to evaluate and manage clinical situations therefore assessment errors can influence the ichosen therapies.

To assess the variability in values of BW obtained by using different equipment (weight scales).

A cross sectional study was performed to assess BW of 360 adult patients in eight units including clinical and surgical specialties Three types of scales were used: a portable domestic model and a fixed platform model, both from the units and a portable digital model previously calibrated and used as standard reference equipment. Self-reported weight (SRW) was also compared to weight assessed with the reference equipment. The values were compared trough paired-samples t-test using SPSS software.

The difference between weights assessed by the reference equipment and SRW was 445+/-3.359 g (P=0.015), it was -182+/-2.323 g (P=0.140) for portable domestic scales and 137+/-2.412 g (P=0.218) for platform fixed scales. Values obtained from SRW, portable domestic scales and fixed platform scales were strongly correlated to the mean value of weight assessed by the reference equipment (r=0.973, r=0.987 and r=0.986, respectively). Nevertheless, considering analyses of each patient, errors of magnitude greater than 500 g occurred in 78.8% of SRW, 80.6% of the portable domestic scales and 40% of the fixed platform scales.

In general, the scales tested were neither accurate nor precise for measuring BW, considering the percentage of error in the evaluation of each patient and the variability observed.