Stability and degradation of fibroblast growth factor 23 (FGF23): the effect of time and temperature and assay type.

UNLABELLED: There is growing need for a reliable assay for measuring fibroblast growth factor 23 (FGF23), a regulator of phosphorus and vitamin D. In this work, we analyze and compare the performance of three available assays, including the effect of temperature and time. This knowledge will allow for better understanding of FGF23 in the future. INTRODUCTION: Intact and C-terminal FGF23 (iFGF23 and cFGF23) concentrations are important in the diagnosis of hypo- and hyperphosphatemic diseases. The effects of temperature, storage, and specimen handling on FGF23 levels are not well known. We investigated the effects of various factors on plasma and serum measurement of FGF23 using three different assays. METHODS: Serum and plasma FGF23 were measured using three commercially available ELISA assays-two measuring iFGF23 and one measuring cFGF23. Samples from subjects with known FGF23 disorders were stored at 4, 22, and 37 °C and analyzed at different intervals up to 48 hours (h). A subset of samples underwent repeated freeze-thaw cycles, and samples frozen at -80 °C for up to 60 months were reanalyzed. The effect of adding a furin convertase inhibitor on FGF23 degradation was investigated using samples stored at 37 °C for 48 h. Intact FGF23 levels were measured from plasma samples of four different groups to test the correlation of the two assays. RESULTS: Plasma FGF23 levels were stable when stored at 4 and 22 °C for 48 h. Both plasma and serum FGF23 levels demonstrated relative stability after five freeze-thaw cycles. Long-term storage at -80 °C for 40 months induced some variability in FGF23 levels. The addition of a furin inhibitor did not affect FGF23 degradation. Intact FGF23 levels showed good correlation only at the upper limit of the assay range when comparing the two assays. CONCLUSIONS: Sample type, handling, and choice of assay are factors that affect FGF23 levels and should be considered when measuring this hormone.

Pain in fibrous dysplasia of bone: age-related changes and the anatomical distribution of skeletal lesions.

UNLABELLED: To determine the prevalence, distribution, age-related changes and treatment of pain in fibrous dysplasia, we studied 78 children and adults. Pain was common, more prevalent and intense in adults, sometimes requiring narcotic analgesia. It was often untreated, especially in children, and surprisingly severity did not correlate with skeletal disease burden. INTRODUCTION: Pain is common in fibrous dysplasia (FD), but relatively unstudied. We studied a well-characterized population of patients with a spectrum of disease. METHODS: Thirty-five children (16 male, 19 female, mean age 11.4 (range 5-18)) and 43 adults (15 male, 28 female, 23-62 yrs, mean age 40.3 (range 23-62)) were studied. Bone scans were used to identify the location and extent of disease. The Brief Pain Inventory was used to determine severity. RESULTS: Pain at sites of FD was common, reported by 67% of the population, but more prevalent and severe in the adult group than the children (81% and 49%, respectively p < 0.005, severity 4.1/10, and 2.8/10, respectively, p < 0.01). Surprisingly, there was no correlation between pain severity and skeletal disease burden. Children were more likely than adults to be untreated for pain (44% vs. 26%). CONCLUSIONS: Pain, which was sometimes severe, was common in subjects with FD. It was often un- or under-treated, especially in children. The prevalence and severity of pain was greater in the adult group, but unrelated to the burden of FD.

Transmission of an azole-resistant isogenic strain of Candida albicans among human immunodeficiency virus-infected family members with oropharyngeal candidiasis.

We report transmission of an azole-resistant, isogenic strain of Candida albicans in a human immunodeficiency virus (HIV)-infected family of two children with symptomatic oropharyngeal candidiasis and a mother with asymptomatic colonization over a 5-year period. These findings were confirmed by three different molecular epidemiology methods: interrepeat PCR, Southern hybridization with a C. albicans repetitive element 2 probe, and electrophoretic karyotyping. This study contributes to an evolving understanding of the mode of transmission of C. albicans, particularly in children, and underscores the importance of monitoring specimens from family members of HIV-infected patients.