Issues of methodology, standardization and metabolite recognition for 25-hydroxyvitamin D when comparing the DiaSorin radioimmunoassay and the Nichols Advantage automated chemiluminescence protein-binding assay in hip fracture cases

BACKGROUND

Deficiency of vitamin D is commonly associated with hip fracture and treatment with vitamin D reduces hip fracture rates. Consequently, the demand for assays to measure 25-hydroxyvitamin D (25-OHD) has increased. The Nichols Advantage chemiluminescence protein-binding assay (CLPBA) for 25-OHD is a first-generation automated immunoassay with decreased turnaround time, reduced manual handling and non-radioactive label.

METHODS

We compared the CLPBA to the DiaSorin radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC) for the measurement of 25-OHD using 161 samples from hip fracture patients and samples before and after institution of ergocalciferol (vitamin D(2)) therapy.

RESULTS

A negative bias for the CLPBA at concentrations below 30 nmol/L and a positive bias at 25-OHD values above 30 nmol/L compared with the RIA resulted in diagnostic discordance for one in three samples when using 30 and 50 nmol/L as decision limits. HPLC analysis confirmed the presence of a negative bias for the CLPBA at low values. Both immunoassays under-estimate 25-hydroxyvitamin D(2).

CONCLUSIONS

The discordance between 25-OHD values may be due to differences in standardization of each assay relative to HPLC. Our results emphasize the need for assay-specific clinical decision limits.

Nutritional supplements after hip fracture: poor compliance limits effectiveness

BACKGROUND

Undernutrition and weight loss are important determinants of clinical outcome in older patients after hip fracture but the effectiveness of nutritional support programs in routine clinical practice remains controversial. AIMS OF THE PROJECT: To determine if oral nutritional supplements given daily for 28 days after hip fracture surgery could prevent weight loss and/or lead to improved clinical outcomes (mortality rates, discharge destination, activities of daily living or length of hospital stay) in non-malnourished community-dwelling older women with hip fracture.

METHODS

One hundred and nine women with BMI range 20-30 kg/m(2) were allocated to either nutritional supplements (352 kcal/day) or usual hospital nutrition using a quasi-randomisation technique. Body weight changes were monitored at 4 and 8 weeks and clinical outcomes were recorded at discharge and at 6 months.

RESULTS

No significant differences in weight change or clinical outcomes were seen between the two groups. Compliance with consuming the nutritional supplements was quite variable and there was a significant negative correlation between the amount of supplement consumed and subsequent weight change (r=-0.36, P=0.019).

CONCLUSIONS

Poor compliance with oral nutritional supplements is an important determinant of the effectiveness of oral nutritional interventions in preventing weight loss after hip fracture. Whilst this may explain the lack of clinical improvements seen, our data do not support the routine use of oral nutritional supplements in non-malnourished hip fracture patients.

Atenolol-induced lupus erythematosus

Atenolol is a beta-blocker commonly used for treating hypertension. It can induce various kinds of adverse side effects, including psoriasiform skin eruptions, skin necrosis, vasculitis, and (rarely) drug-induced connective tissue disease. We encountered a patient receiving atenolol for his hypertension for 3 years who subsequently acquired connective tissue disease and antihistone antibodies. The initial serologic antinuclear antibody test was negative at a dilution of 1/20 but was positive after further serial dilutions, indicating the prozone phenomenon as the cause of the false-negative result. Six months after discontinuation of atenolol, the skin rash disappeared and antihistone antibody subsided. His skin rash reappeared on rechallenge with atenolol for 3 days, confirming that atenolol was responsible for his lupus erythematosus.