Introduction Weight estimation of both adult and paediatric patients is often necessary in emergency or low-resource settings when it is not possible to weigh the patient. There are many methods for paediatric weight estimation, but no standard methods for adults. PAWPER and Mercy tapes are used in children, but have not been assessed in adults. The primary aim of this study was to assess weight estimation methods in patients of all ages.

Methods Patients were prospectively recruited from emergency and outpatient departments in Kigali, Rwanda. Participants (or guardians) were asked to estimate weight. Investigators collected weight, height, mid-arm circumference (MAC) and humeral-length data. In all participants, estimates of weight were calculated from height and MAC (PAWPER methods), MAC and humeral length (Mercy method). In children, Broselow measurements and age-based formulae were also used. The primary outcome measure was the proportion of estimates within 20% of actual weight (p20).

Results We recruited 947 participants: 307 children, 309 adolescents and 331 adults. For p20, the best methods were: in children, guardian estimate (90.2%) and PAWPER XL-MAC (89.3%); in adolescents, PAWPER XL-MAC (91.3%) and guardian estimate (90.9%); in adults, participant estimate (98.5%) and PAWPER XL-MAC (83.7%). In all age groups, there was a trend of decreasing weight estimation with increasing actual weight.

Conclusion This prospective study of weight estimation methods across all age groups is the first adult study of PAWPER and Mercy methods. In children, age-based rules performed poorly. In patients of all ages, the PAWPER XL-MAC and guardian/participant estimates of weight were the most reliable and we would recommend their use in this setting.