Journal of the New Zealand Medical Association. NZMJ 28 November 2008, Vol 121 No ... Auckland District Health Board laboratories. The laboratory uses the ...
THE NEW ZEALAND MEDICAL JOURNAL Journal of the New Zealand Medical Association
Prevalence of vitamin D deficiency among patients attending a multidisciplinary tertiary pain clinic Jim Bartley Abstract Aim To estimate the prevalence of vitamin D deficiency in a tertiary multidisciplinary pain clinic. Methods From 14 July 2006 to 30 November 2007, the author requested vitamin D status from all patients with chronic persistent pain presenting to The Auckland Regional Pain Service (a tertiary multidisciplinary pain service). Serum 25hydroxyvitamin D levels were determined by radioassay. Results Of 177 patients, 3% had 25-hydroxyvitamin D levels ≤17.5 nmol/L—a level associated with osteomalacia, 32% had 25-hydroxyvitamin D levels ≤50 nmol/L—a level associated with vitamin D deficiency, and 73% had 25-hydroxyvitamin D levels ≤80 nmol/L. Conclusions The prevalence of vitamin D deficiency in patients attending a multidisciplinary pain clinic is similar to if not less than that of the normal New Zealand population. Recent African immigrants and south Asian females are two patient groups that are frequently vitamin D deficient. The identification and treatment of vitamin D deficiency has the theoretical potential to help a number of chronic pain patients. Only a limited number of interventional clinical trials have looked at this. Vitamin D deficiency has been increasingly implicated in a number of pain syndromes. Pain refractory to narcotics is well recognised in severe vitamin D deficiency.1 Plotnikoff and Quigley have documented that vitamin D deficiency is common in patients presenting with persistent non-specific musculoskeletal pain in a primary care setting.2 In New Zealand, Chiu has reported that vitamin D deficiency is common in a private rheumatology practice.3 Similarly vitamin D deficiency has been reported in pain syndromes such as low back pain,4 migraine,5 and diabetic peripheral neuropathy.6 Because of these observations, a survey was conducted to determine the prevalence of vitamin D deficiency among patients attending a tertiary multidisciplinary pain clinic.
Methods All new patients presenting to the author as part of their initial evaluation had their 25-hydroxyvitamin D level requested. Pathology forms were given to patients and the assay was performed by the Auckland District Health Board laboratories. The laboratory uses the Diasorin assay kit, which has a coefficient of variation of 6% between tests which approximates to ±12% for confidence limits. Those patients already taking colecalciferol were excluded from the survey. Because 25-hydroxyvitamin D measurement is an expensive test, if 25-hydroxyvitamin D levels had been measured in the previous 3 months, the test was not repeated. These patients were still included in the survey if they had not been treated.
NZMJ 28 November 2008, Vol 121 No 1286; ISSN 1175 8716 URL: http://www.nzma.org.nz/journal/121-1286/3380/
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Within the pain clinic, a number of doctors have specific pain interests. While a broad range of pain conditions were seen, the population assessed reflected the author’s particular interest in facial pain.
Results From 14 July 2006 to 30 November 2007, the author saw 187 patients. Two patients did not have their 25-hydroxyvitamin D levels measured. Three patients did not have their 25-hydroxyvitamin D levels done because they were already taking colecalciferol. Patients taking multivitamin supplements, which can include low doses of vitamin D, were included in the survey. Another patient with a previous vitamin D level consistent with osteomalacia (13 nmol/L) had stopped her medication 6 months earlier. Four additional patients taking colecalciferol 1.25 mg monthly, where there were still concerns about their vitamin D status, had their 25-hydroxyvitamin D levels checked. One of these patients despite taking replacement therapy had a 25hydroxyvitamin D level of 33 nmol/L. These ten patients were not included in the survey. Two patients who had had their 25-hydroxyvitamin D levels done in the 3 months prior to being seen at the pain clinic were included. Female patients comprised 66% of the patients seen. Of the 177 eligible patients who had 25-hydroxyvitamin D levels performed 3% had levels ≤17.5nmol/L—a level associated with osteomalacia, 32% had levels ≤ 50nmol/L—a level associated with vitamin D deficiency, and 73% had levels ≤80nmol/L. No seasonal variation was observed. The majority of the patients seen were European. Four patients were of African ethnicity (average 25-hydroxyvitamin D level—25 nmol/L); 14 patients were South East Asian (average vitamin D level—54 nmol/L); 17 patients were South Asian (average vitamin D— 65 nmol/L; 80% of the females had levels less than 50 nmol/L); 7 patients were from the Middle East (average vitamin D level—47 nmol/L); 6 patients were from the Pacific Islands (average vitamin D level—40 nmol/L); and 10 patients identified themselves as Māori (average vitamin D level—54 nmol/L). The average 25-hydroxyvitamin D level of those referred specifically with low back pain (20 patients) was 54 nmol/L. Of those patients with vitamin D levels ≤17.5nmol/L, a level typically associated with osteomalacia, all were female with a wide range of age ranges being represented (Table 1). Vitamin D deficiency was observed in all age groups with a slight female predominance (Figure 1). Table 1. Race, sex and age of those patients whose 25-hydroxyvitamin D levels were less than 17.5 nmol/L (n=6) Ethnicity Middle East South Asian European African Māori South Asian
Sex
Age
Female Female Female Female Female Female
35 48 80 39 51 32
25-hydroxyvitamin D level (nmol/L) 13 13 11 12 16 16
NZMJ 28 November 2008, Vol 121 No 1286; ISSN 1175 8716 URL: http://www.nzma.org.nz/journal/121-1286/3380/
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Figure 1. Vitamin D level (nmol/L) by age, sex, and ethnicity (European/nonEuropean) in patients with vitamin D deficiency (25-hydroxyvitamin ≤50 nmol/L)
Discussion This survey has shown that vitamin D deficiency is common in patients attending a multidisciplinary pain clinic, however the prevalence of vitamin D deficiency is similar if not less than that seen in the general New Zealand population. In a recent national sample of 2946 New Zealanders aged 15 years and over, 84% of people had a mean serum 25-hydroxyvitamin D concentration of ≤80 nmol/L, 48% had levels of ≤50 nmol/L, and 3% had levels of ≤17.5 nmol/L. Mean serum 25hydroxyvitamin D levels were 5 nmol/L lower in females and were lower in the South Island. Mean serum 25-hydroxyvitamin D levels were also lower in Maori (42 nmol/L) and Pacific Island people (37 nmol/L) compared to people of other ethnicities (51 nmol/L).7 An Auckland survey in women ≥55 years of predominantly Caucasian/European women found a high prevalence of vitamin D deficiency even in summer.8 In a similar Auckland survey in predominantly European men, 9% of men had vitamin D levels
