Precision in weighing: a comparison of scales found in physician offices, fitness centers, and weight loss centers.
OBJECTIVE
Weight assessment is a critical aid in patient care. It is particularly important in monitoring progression of pregnancies, heart failure status, and when adjusting medications. Although weight is generally determined using a scale, few studies have evaluated the precision of non-household scales. The objective of this study was to assess scale precision across a variety of settings.


METHODS
An evaluation of scales from randomly selected primary care clinics (n=30), diabetology/endocrinology clinics (n=7), weight loss facilities (n=25), and fitness centers (n=30) was performed. Assessments were completed on a total of 223 scales: 94 from primary care clinics, 32 from diabetology/endocrinology clinics, 39 from weight loss centers, and 58 from fitness centers. Scales were assessed for condition, location in facility, resting surface, commercial designation, and calibration history. Scale precision was validated using 100 lb. (45.5 kg), 150 lb. (68.3 kg), 200 lb. (90.9 kg), and 250 lb. (113.6 kg) certified weights.


RESULTS
Overall, scales demonstrated decreased precision with increased weight. At higher weights, more than 15% of scales were off by more than 6 lbs. (2.3 kg), approximately 1 Body Mass Index (BMI) unit. While facility type was not significant, condition, location in facility, resting surface, commercial designation, and calibration history were significant.


CONCLUSIONS
This study demonstrates that many scales used to measure body weight are imprecise and that scales in health care settings are no more precise than those in other facilities. Clinical decisions based on scales that are imprecise have the potential to cause iatrogenic complications in patient care.
Stein
Risa J
RJ
Department of Psychology, Rockhurst University, Kansas City, MO 64110, USA. risa.stein@rockhurst.edu
Haddock
C Keith
CK
Poston
Walker S C
WS
Catanese
Dana
D
Spertus
John A
JA
D000554:Ambulatory Care Facilities; D015992:Body Mass Index; D001835:Body Weight; D002138:Calibration / Q000592:standards*; D004704:Endocrinology; D004864:Equipment and Supplies / Q000592:standards*; D005260:Female; D020446:Fitness Centers; D006294:Health Resorts; D006801:Humans; D008297:Male; D008923:Missouri; D010824:Physicians' Offices; D011320:Primary Health Care