Endocrine Abstracts

Background: Recent consensus recommends assessment of aortic dimensions with aortic sized index (ASI) normalized for body surface area (BSA) defined as absolute aortic dimension/BSA, in girls with Turner syndrome (TS) as young as 10 years. There are currently multiple formulae for estimating BSA without agreement on a preferred method. We assess the clinical validity of each formulae as this may have implications on interpretation of ASI.

Method: We calculated BSA using Dubois, Mostellar, Haycock (height and weight based) and Furqan (weight based) formulae from 114 girls with TS with height and weight measurements from 2273 outpatient visits. The mean of all four equations was used as gold standard and the mean error (lower limit and upper limit) for each individual formula calculated.

Results: All formulae were highly agreeable, with Mosteller (mean error −0.007, −0.021 to 0.007), and Haycock (mean error 0.001, −0.014 to 0.016) having all estimations accurate to within 5%. 3.9% of Dubios and 9.6% Furqan estimations of BSA had >5% error. Dubois underestimates BSA in heavier girls. Mostellar underestimates BSA in older, heavier, and taller girls. Haycock overestimates BSA in younger, lighter, shorter girls then underestimates but also overestimates in older, heavier, and taller girls. Furqan overestimates BSA in older heavier, and taller girls. Mean BSA (S.D.) in TS are: 8 years 0.90 cm/m m² (0.10); 10 years 1.01 m² (0.13); 12 years 1.19 m² (0.16); 14 years 1.37 m² (0.19); and 16 years 1.51 m² (0.21) (P< 0.0001).

Conclusion: Our study demonstrated for the first time that Dubois, Mosttellar, Haycock, and Furqan formulae perform just as well for estimation of BSA in girls with TS, although under and overestimation can occur in specific situations. BSA increases in a non-linear fashion from the age of 8 years in TS. The clinical implications of this on interpretation of longitudinal changes ASI in growing children with TS need to be validated in future studies.