Poster Presentation Joint Annual Scientific Meeting of the Nutrition Society of NZ and the Nutrition Society of Australia

Can questionnaire-based tools to predict vitamin D deficiency replace blood testing for New Zealand preschool children? (#P7)

Carolyn Cairncross 1 , Barry McDonald 1 , Welma Stonehouse 2 , Cath A Conlon 1 , Cameron C Grant 3 , Lisa A Houghton 4 , Darryl Eyles 5 , Carlos Camargo Jnr 6 , Jane Coad 1 , Pamela R von Hurst 1
  1. Massey University, Auckland, New Zealand
  2. CSIRO, Adelaide, Australia
  3. University of Auckland, Auckland, New Zealand
  4. University of Otago, Dunedin, New Zealand
  5. University of Queensland, Brisbane, Australia
  6. Massachusetts General Hospital, Boston, USA

Background/Aims: Timely identification and treatment of children with vitamin D deficiency is important. However, vitamin D status determined through serum 25(OH)D sampling can be painful for young children and is not routinely funded in New Zealand. Predictive questionnaire-based tools offer a non-invasive alternative.  Our objective was to develop a questionnaire-based tool to predict vitamin D deficiency in NZ preschool-aged children.

Methods: Dried capillary blood spots were collected from 1329 children during late winter to early spring for 25(OH)D measurement by LC-MS/MS. Caregivers completed a questionnaire describing their child’s demographics and factors known to affect vitamin D status. Predictors of 25(OH)D<25nmol/L and 25(OH)D<50nmol/L were identified using multivariable logistic regression in a randomly-selected sub-sample (n=929) for development of two predictive tools, which then were validated by receiver operating characteristics (ROC) analysis (n=400).  

Results: Serum 25(OH)D levels were <25nmol/L in 7% of children and <50nmol/L in 49%. The tool predicting 25(OH)D <25nmol/L had a sensitivity of 42%, specificity 97% and AUC 0.76 (95%CI 0.67-0.86,P<0.001). The tool predicting 25(OH)D <50nmol/L had a sensitivity of 52%, specificity 66% and AUC 0.63 (95%CI 0.57-0.68,P<0.001).

Conclusions: Despite the large sample size, the questionnaire-based tools were unable to accurately predict vitamin D deficiency in these preschool-aged children, suggesting that blood 25(OH)D testing be used to determine vitamin D status. Further research into safe and inexpensive methods of assessing vitamin D status in vulnerable populations is indicated.

Funding source: Health Research Council of New Zealand