[1] Univ Auckland, Fac Med & Hlth Sci, Sect Biostat & Epidemiol, M&HD Bldg 507,28 Pk Ave, Auckland 1023, New Zealand
[2] Auckland City Hosp, LabPlus, Auckland, New Zealand
[3] Univ Auckland, Fac Med & Hlth Sci, Sect Pacific Hlth, Auckland, New Zealand
[4] Univ Auckland, Fac Med & Hlth Sci, Dept Pediat Child & Youth Hlth, Auckland, New Zealand