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Iodine Status Assessment in South African Adults According to Spot Urinary Iodine Concentrations, Prediction Equations, and Measured 24-h Iodine Excretion

Journal Article


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Abstract


  • The iodine status of populations is conventionally assessed using spot urinary samples

    to obtain a median urinary iodine concentration (UIC) value, which is assessed against standard

    reference cut-offs. The assumption that spot UIC reflects daily iodine intake may be flawed because

    of high day-to-day variability and variable urinary volume outputs. This study aimed to compare

    iodine status in a sample of South African adults when determined by different approaches using

    a spot urine sample (median UIC (MUIC), predicted 24 h urinary iodine excretion (PrUIE) using

    different prediction equations) against measured 24 h urinary iodine excretion (mUIE). Both 24 h

    and spot urine samples were collected in a subsample of participants (n = 457; median age 55 year;

    range 18–90 year) in theWorld Health Organization Study on global AGEing and adult health (SAGE)

    Wave 2 in South Africa, in 2015. Kawasaki, Tanaka, and Mage equations were applied to assess

    PrUIE from predicted urinary creatinine (PrCr) and spot UIC values. Adequacy of iodine intake

    was assessed by comparing PrUIE and mUIE to the Estimated Average Requirement of 95 μg/day,

    while the MUIC cut-off was <100 μg/L. Bland Altman plots assessed the level of agreement between

    measured and predicted UIE. Median UIC (130 μg/L) indicated iodine sufficiency. The prediction

    equations had unacceptable bias for PrUIE compared to measured UIE. In a sample of adult South

    Africans, the use of spot UIC, presented as a group median value (MUIC) provided similar estimates

    of inadequate iodine status, overall, when compared to EAR assessed using measured 24 h iodine

    excretion (mUIE). Continued use of MUIC as a biomarker to assess the adequacy of population iodine

    intake appears warranted.

Authors


  •   Charlton, Karen E.
  •   Ware, Lisa J. (external author)
  •   Baumgartner, Jeannine (external author)
  •   Cockeran, M (external author)
  •   Schutte, Aletta E. (external author)
  •   Naidoo, Nirmala (external author)
  •   Kowal, Paul (external author)

Publication Date


  • 2018

Citation


  • Charlton, K. E., Ware, L. J., Baumgartner, J., Cockeran, M., Schutte, A. E., Naidoo, N. & Kowal, P. (2018). Iodine Status Assessment in South African Adults According to Spot Urinary Iodine Concentrations, Prediction Equations, and Measured 24-h Iodine Excretion. Nutrients, 10 (6), e736-1-e736-14.

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1012&context=smhpapers1

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers1/13

Start Page


  • e736-1

End Page


  • e736-14

Volume


  • 10

Issue


  • 6

Place Of Publication


  • Switzerland

Abstract


  • The iodine status of populations is conventionally assessed using spot urinary samples

    to obtain a median urinary iodine concentration (UIC) value, which is assessed against standard

    reference cut-offs. The assumption that spot UIC reflects daily iodine intake may be flawed because

    of high day-to-day variability and variable urinary volume outputs. This study aimed to compare

    iodine status in a sample of South African adults when determined by different approaches using

    a spot urine sample (median UIC (MUIC), predicted 24 h urinary iodine excretion (PrUIE) using

    different prediction equations) against measured 24 h urinary iodine excretion (mUIE). Both 24 h

    and spot urine samples were collected in a subsample of participants (n = 457; median age 55 year;

    range 18–90 year) in theWorld Health Organization Study on global AGEing and adult health (SAGE)

    Wave 2 in South Africa, in 2015. Kawasaki, Tanaka, and Mage equations were applied to assess

    PrUIE from predicted urinary creatinine (PrCr) and spot UIC values. Adequacy of iodine intake

    was assessed by comparing PrUIE and mUIE to the Estimated Average Requirement of 95 μg/day,

    while the MUIC cut-off was <100 μg/L. Bland Altman plots assessed the level of agreement between

    measured and predicted UIE. Median UIC (130 μg/L) indicated iodine sufficiency. The prediction

    equations had unacceptable bias for PrUIE compared to measured UIE. In a sample of adult South

    Africans, the use of spot UIC, presented as a group median value (MUIC) provided similar estimates

    of inadequate iodine status, overall, when compared to EAR assessed using measured 24 h iodine

    excretion (mUIE). Continued use of MUIC as a biomarker to assess the adequacy of population iodine

    intake appears warranted.

Authors


  •   Charlton, Karen E.
  •   Ware, Lisa J. (external author)
  •   Baumgartner, Jeannine (external author)
  •   Cockeran, M (external author)
  •   Schutte, Aletta E. (external author)
  •   Naidoo, Nirmala (external author)
  •   Kowal, Paul (external author)

Publication Date


  • 2018

Citation


  • Charlton, K. E., Ware, L. J., Baumgartner, J., Cockeran, M., Schutte, A. E., Naidoo, N. & Kowal, P. (2018). Iodine Status Assessment in South African Adults According to Spot Urinary Iodine Concentrations, Prediction Equations, and Measured 24-h Iodine Excretion. Nutrients, 10 (6), e736-1-e736-14.

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1012&context=smhpapers1

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers1/13

Start Page


  • e736-1

End Page


  • e736-14

Volume


  • 10

Issue


  • 6

Place Of Publication


  • Switzerland