Vitamin D status of adults from tropical Australia determined using two different laboratory assays: implications for public health messages

We measured serum 25 hydroxyvitamin D 25(OH)D] levels of ambulatory adults in tropical Australia to determine whether it is appropriate to continue promoting sun‐safety in this population. In August 2006 (winter), self‐administered questionnaires were completed by 145 Meals‐on‐Wheels volunteers (49.3% male; mean age 57.8 ± 14.7 years; 76.6% response) from Townsville, Queensland (Latitude 19^oS). Serum 25(OH)D was analyzed using two common assays. Mean levels were 68.3 (SD ± 18.7; range 26–142) by DiaSorin Radioimmunoassay and 83.0 (SD ± 30.8; range 30–184) by DiaSorin Liaison^® one. No participants were 25(OH)D deficient (<25 nmol L^?1). Nine participants (6.2%) had 25(OH)D levels between 25 and 50 nmol L^?1 (insufficient), by both methods (seven with a BMI ≥ 25). Twenty‐eight participants (19.3%) had one result in the insufficient range and the other in the adequate range. Thus, almost all of these free‐living adults in tropical Australia had adequate vitamin D levels at the end of winter. There was poor agreement between the two 25(OH)D assays. These results suggest it is appropriate to continue promoting sun‐safe messages to the ambulatory Caucasian adult population of North Queensland, which has an extremely high incidence of skin cancer. The lack of agreement between the two assays is a concern. Few doctors are aware of this measurement issue.