Chi squared testing was used to assess differences in the percentage of patients whose estimated weights fell within 10% of measured weight using different formulae. The data was collected and tabulated using a Microsoft Excel 2007 spreadsheet. Microsoft Excel 2007 was also used to calculate percentage differences

and mean values and to create the graphical representation of the data. Epi Info v. 3.5 was used to calculate standard deviations, confidence Staurosporine intervals and to perform linear regression analysis. Results 1784 patients met the eligibility criteria for the study. Of these, 45 (2.5%) were excluded Inhibitors,research,lifescience,medical due to weight not being documented in the record and 6 (0.3%) were excluded due to illegible entries. 1723 patients were included in the final analysis. Using linear Inhibitors,research,lifescience,medical regression analysis, the best formula to describe weight and age was as follows: Weight=2.40 × age+8.25. This formula, however, is impractical for use in the Emergency Department due to difficulty for quick calculation. Another more applicable formula would be: Weight=2.5 × age+8. The APLS formula, the Luscombe and Owens formula ([3 × age] Inhibitors,research,lifescience,medical +7) and the newly derived formula ([2.5 × age]+8) were compared. The results are shown in Table ​Table11. Table 1 Comparison of APLS, Luscome and Owens and new derived

formula using Bland-Altman method The APLS formula underestimated weight in all age groups with a mean difference (bias) of −1.4kg (95% limits of agreement 5.0 to −7.8). This was most pronounced in the 5year old age group with a mean difference of −2.4kg (95%

limits of agreement 6.6 to −9.4) and least pronounced in the 1year old age group with a mean difference of −0.6kg (95% limits of agreement 3.1 to −4.4). The Luscombe and Owens formula was slightly more accurate in predicting weight than the APLS Inhibitors,research,lifescience,medical formula overall with a mean difference Inhibitors,research,lifescience,medical of −0.4kg (95% limits of agreement 6.9 to −6.1) (Table ​(Table1).1). The derived formula was the most accurate in predicting weight, with all age groups having an error of less than 10% with an overall underestimation of −0.4kg (95% limits of agreement 6.9 to −6.1). The Bland-Altman graphs for each estimated weight formula are shown in Additional Annual Review of Physiology file 2. Accuracy was also compared by calculating the percentage differences between the estimated weights from each formula and the measured (actual) weights of the patients. The overall percentage difference between the estimated weights using the APLS formula compared to the actual weights was −5.8% (95% confidence intervals −5.0 to −6.6). This difference was least marked in the 1year age group and most marked in the 5year age group. The overall percentage difference between the estimated weights using the Luscombe and Owens formula and the actual weights was +5.0% (95% confidence intervals 4.1 to 5.9). Again, the difference was more marked with the older age groups of children. The derived formula was most accurate, with a percentage variation of −3.1% (95% confidence intervals −3.9 to −2.3).