Serum 25-hydroxyvitamin D threshold and risk of rickets in young children: a systematic review and individual participant data meta-analysis to inform the development of dietary requirements for vitamin D

PURPOSE

The objective of this systematic review was to determine a minimum serum 25-hydroxyvitamin D (25OHD) threshold based on the risk of having rickets in young children. This work was commissioned by the WHO and FAO within the framework of the update of the vitamin D requirements for children 0-3 years old.

METHODS

A systematic search of Embase was conducted to identify studies involving children below  4 years of age with serum 25OHD levels and radiologically confirmed rickets, without any restriction related to the geographical location or language. Study-level and individual participant data (IPD)-level random effects multi-level meta-analyses were conducted. The odds, sensitivity and specificity for rickets at different serum 25OHD thresholds were calculated for all children as well as for children with adequate calcium intakes only.

RESULTS

A total of 120 studies with 5412 participants were included. At the study-level, children with rickets had a mean serum 25OHD of 23 nmol/L (95% CI 19-27). At the IPD level, children with rickets had a median and mean serum 25OHD of 23 and 29 nmol/L, respectively. More than half (55%) of the children with rickets had serum 25OHD below 25 nmol/L, 62% below 30 nmol/L, and 79% below 40 nmol/L. Analysis of odds, sensitivities and specificities for nutritional rickets at different serum 25OHD thresholds suggested a minimal risk threshold of around 28 nmol/L for children with adequate calcium intakes and 40 nmol/L for children with low calcium intakes.

CONCLUSION

This systematic review and IPD meta-analysis suggests that from a public health perspective and to inform the development of dietary requirements for vitamin D, a minimum serum 25OHD threshold of around 28 nmol/L and above would represent a low risk of nutritional rickets for the majority of children with an adequate calcium intake.

Analysis of vitamin D3-sulfate and 25-hydroxyvitamin D3-sulfate in breastmilk by LC-MS/MS

Sulfated metabolites of vitamin D have been suggested to be in breastmilk, although current methods to measure sulfated vitamin D compounds in breastmilk by liquid chromatography-tandem mass spectrometry (LC-MS/MS) have not adequately accounted for increased aqueous solubility of these sulfated metabolites. The purpose of this study was to generate a method of LC-MS/MS for measuring vitamin D3-3-sulfate (VitD3-S) and 25-hydroxyvitamin D3-3-sulfate (25OHD3-S) specifically in human breastmilk. The resulting method uses methanol to precipitate protein and solid phase extraction to prepare the samples for LC-MS/MS. The limits of quantification for analytes in solvent were 0.23 ng/mL VitD3-S and 0.2 ng/mL 25OHD3-S. Various experiments observed concentrations ranging 0.53 to 1.7 ng/mL VitD3-S and ≤ 0.29 ng/mL 25OHD3-S. Both analytes were present in aqueous skim milk, demonstrating the enhanced aqueous solubility of these vitamin D sulfates. In conclusion, we describe an effective method for measuring VitD3-S and 25OHD3-S in breastmilk by LC-MS/MS.

Arsenic Exposure in Well Water From the Perspective of Patients and Providers

BACKGROUND

Arsenic is a well-known toxin which may contaminate household water. It is harmful when ingested over prolonged periods of time. As a result, public health experts recommend that water should be screened and treated to prevent arsenic ingestion. In the United States, the responsibility of testing and treatment of private wells falls on homeowners. Despite recommendations for routine screening, this is rarely done.

OBJECTIVES

To assess the prevalence of well water use in a Midwestern patient population, how patients and clinicians perceive the risks of arsenic in well water, and whether additional resources on well water testing are desired. These findings will be used to influence tools for clinicians regarding symptom and examination findings of chronic arsenic exposure and potentiate the distribution of informational resources on well water testing.

METHODS

Surveys were sent via email to all actively practicing primary care clinicians at the Mayo Clinic in the United States Midwest, and all active adult patients at the Mayo Clinic in the same region. Our team analyzed survey data to determine whether both patients and clinicians are aware of the health effects of chronic arsenic toxicity from well water, the need for routine well water testing and whether each group wants more information on the associated risks.

RESULTS

Both patients and primary care clinicians worry about arsenic exposure. Patients with well water are concerned about their water safety yet feel uninformed about testing options. Clinicians do not know how prevalent well water use is among their patients, feel uninformed about the chronic risks of arsenic exposure and the physical examination associated with it. Both groups unanimously want more information on testing options.

CONCLUSIONS

Our findings show a significant reliance on well water use in the American Midwest, and unanimous support for the need for further well water testing information and resources for patients and their clinicians.

Vitamin D: immune function, inflammation, infections and auto-immunity

Vitamin D plays an active role beyond mineral metabolism and skeletal health, including regulation of the immune system. Vitamin D deficiency is widely prevalent, and observational studies link low vitamin D status to a risk of infections and auto-immune disorders. Reports indicate an inverse relationship between vitamin D status and such conditions. This review details vitamin D signalling interactions with the immune system and provides experimental and clinical evidence evaluating vitamin D status, vitamin D supplementation and host susceptibility to infections, inflammation and auto-immunity. The published literature including related reviews, systematic reviews, meta-analyses, randomised controlled trials (RCTs), observational studies and basic science reports have been synthesised. Meta-analyses of observational studies have demonstrated a link between low vitamin D status and risk of acute respiratory infections, COVID-19 disorders, multiple sclerosis, type 1 diabetes (T1DM), inflammatory bowel disease (IBD), systemic lupus erythematosus and other auto-immune disorders. Observational studies suggest that vitamin D supplementation may protect against several infectious and auto-immune conditions. Meta-analyses of RCTs had mixed results, demonstrating a small protective role for vitamin D supplementation against acute respiratory infections, especially in those with vitamin D deficiency and children, and providing modest benefits for the management of T1DM and IBD. Vitamin D status is inversely associated with the incidence of several infectious and auto-immune conditions. Supplementation is recommended for those with vitamin D deficiency or at high risk of deficiency, and it might provide additional benefit in acute respiratory infections and certain auto-immune conditions.

Disparities in Diabetes Care: Differences Between Rural and Urban Patients Within a Large Health System

PURPOSE

We sought to ascertain factors associated with the quality of diabetes care, comparing rural vs urban diabetic patients in a large health care system.

METHODS

We conducted a retrospective cohort study assessing patients' attainment of the D5 metric, a diabetes care metric having 5 components (no tobacco use, glycated hemoglobin [A_1c] level less than 8%, blood pressure less than 140/90 mm Hg, low-density lipoprotein cholesterol level at goal or statin prescribed, and aspirin use consistent with clinical recommendations). Covariates included age, sex, race, adjusted clinical group (ACG) score as a marker of complexity, insurance type, primary care clinician type, and health care use data.

RESULTS

The study cohort consisted of 45,279 patients with diabetes, 54.4% of whom resided in rural locations. The D5 composite metric was met in 39.9% of rural patients and 43.2% of urban patients (P <.001). Rural patients were significantly less likely to have attained all metric goals than urban counterparts (adjusted odds ratio [AOR] = 0.93; 95% CI, 0.88-0.97). The rural group had fewer outpatient visits (mean number of visits = 3.2 vs 3.9, P <.001) and less often had an endocrinology visit (5.5% vs 9.3%, P <.001) during the 1-year study period. Patients with an endocrinology visit were less likely to have met the D5 metric (AOR = 0.80; 95% CI, 0.73-0.86), whereas the more outpatient visits patients had, the greater their likelihood of attainment (AOR per visit = 1.03; 95% CI, 1.03-1.04).

CONCLUSIONS

Rural patients had worse diabetes quality outcomes than their urban counterparts, even after adjustment for other contributing factors and despite being part of the same integrated health system. Lower visit frequency and less specialty involvement in the rural setting are possible contributing factors.

Highlights from the 24th workshop on vitamin D in Austin, September 2022

The 24th Workshop on Vitamin D was held September 7-9, 2022 in Austin, Texas and covered a wide diversity of research in the vitamin D field from across the globe. Here, we summarize the meeting, individual sessions, awards and presentations given.

Serum 1,25-dihydroxyvitamin D levels in the diagnosis and pathogenesis of nutritional rickets - a multivariable re-analysis of a case-control study

BACKGROUND

A multivariable logistic regression model resulting from a case-control study of nutritional rickets in Nigerian children suggested that higher levels of serum 25(OH)D may be required to prevent nutritional rickets in populations with low-calcium intakes.

OBJECTIVES

This current study evaluates if adding serum 1,25-dihydroxyvitamin D [1,25(OH)₂D] to that model shows that increased levels of serum 1,25(OH)₂D are independently associated with risk of children on low-calcium diets having nutritional rickets.

METHODS

Multivariable logistic regression analysis was used to model the association between serum 1,25(OH)₂D and risk of having nutritional rickets in cases (n = 108) and controls (n = 115) after adjusting for age, sex, weight-for age z-score, religion, phosphorus intake and age began walking and the interaction between serum 25(OH)D and dietary calcium intake (Full Model).

RESULTS

Serum 1,25(OH)₂D levels were significantly higher (320 pmol/L vs. 280 pmol/L) (P = 0.002), and 25(OH)D levels were lower (33 nmol/L vs. 52 nmol/L) (P < 0.0001) in children with rickets than in control children. Serum calcium levels were lower in children with rickets (1.9 mmol/L) than in control children (2.2 mmol/L) (P < 0.001). Dietary calcium intakes were similarly low in both groups (212 mg/d) (P = 0.973). In the multivariable logistic model, 1,25(OH)₂D was independently associated with risk of having rickets [coefficient = 0.007 (95% confidence limits: 0.002-0.011)] after adjusting for all variables in the Full Model.

CONCLUSIONS

Results confirmed theoretical models that in children with low dietary calcium intake, 1,25(OH)₂D serum concentrations are higher in children with rickets than in children without rickets. The difference in 1,25(OH)₂D levels is consistent with the hypothesis that children with rickets have lower serum calcium concentrations which prompt the elevation of PTH levels resulting in an elevation of 1,25(OH)₂D levels. These results support the need for additional studies to identify dietary and environmental risks for nutritional rickets.

Clinician Adoption of an Artificial Intelligence Algorithm to Detect Left Ventricular Systolic Dysfunction in Primary Care

OBJECTIVE

To compare the clinicians' characteristics of "high adopters" and "low adopters" of an artificial intelligence (AI)-enabled electrocardiogram (ECG) algorithm that alerted for possible low left ventricular ejection fraction (EF) and the subsequent effectiveness of detecting patients with low EF.

METHODS

Clinicians in 48 practice sites of a US Midwest health system were cluster-randomized by the care team to usual care or to receive a notification that suggested ordering an echocardiogram in patients flagged as potentially having low EF based on an AI-ECG algorithm. Enrollment was between June 26, 2019, and July 30, 2019; participation concluded on March 31, 2020. This report is focused on those clinicians randomized to receive the notification of the AI-ECG algorithm. At the patient level, data were analyzed for the proportion of patients with positive AI-ECG results. Adoption was defined as the clinician order of an echocardiogram after prompted by the alert.

RESULTS

A total of 165 clinicians and 11,573 patients were included in this analysis. Among patients with positive AI-ECG, high adopters (n=41) were twice as likely to diagnose patients with low EF (33.9%) vs low adopters, n=124, (16.9%); odds ratio, 1.62; 95% CI, 1.21 to 2.17). High adopters were more often advanced practice providers (eg, nurse practitioners and physician assistants) vs physicians, Family Medicine vs Internal Medicine specialty, and tended to have less complex patients.

CONCLUSION

Clinicians who most frequently followed the recommendations of an AI tool were twice as likely to diagnose low EF. Those clinicians with less complex patients were more likely to be high adopters.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT04000087.

Evaluating the Evidence in Clinical Studies of Vitamin D in COVID-19

Laboratory evidence provides a biological rationale for the benefits of vitamin D in COVID-19, and vitamin D supplementation is associated with reduced risk of respiratory infections. Most of the clinical studies of vitamin D in COVID-19 have been observational, and the most serious problem with observational study design is that of confounding. Observational studies typically assess the relationship of 25(OH)D values with COVID-19 outcomes. Many conditions associated with low vitamin D status are also associated with worse COVID-19 outcomes. Randomized controlled trials (RCTs) overcome the problem of confounding, typically comparing outcomes between groups receiving vitamin D supplementation or placebo. However, any benefit of vitamin D in COVID-19 may be related to the dose, duration, daily vs. bolus administration, interaction with other treatments, and timing of administration prior to or during the illness. Serum 25(OH)D values >50 nmol/L have been associated with reduced infection rates, severity of COVID-19, and mortality in observational studies. Few RCTs of vitamin D supplementation have been completed, and they have shown no benefit of vitamin D in hospitalized patients. Vitamin D may benefit those with mild or asymptomatic COVID-19, and those with greater 25(OH)D values may have lower risk of acquiring infection. Because those at greatest risk of COVID-19 are also at greatest risk of vitamin D deficiency, it is reasonable to recommend vitamin D supplementation 15−20 mcg (600−800 IU) daily for the general population during the COVID-19 pandemic. Vitamin D doses greater than 100 mcg (4000 IU) daily should not be used without monitoring serum 25(OH)D and calcium.

Association of Perinatal Factors With Severe Obesity and Dyslipidemia in Adulthood

Background:

Perinatal factors including gestational age, birthweight, size for gestational age, delivery route, maternal parity, maternal age, maternal education, socioeconomic status, race, and sex, are associated with the future risk of obesity and co-morbid conditions. This study evaluated the relationship of birthweight for gestational age and perinatal factors with severe obesity and dyslipidemia in adulthood.

Methods:

We conducted a population-based, retrospective birth cohort study of infants born to residents of Olmsted County, MN between 1976 and 1982. Outcomes were assessed after age 18 years until October 2020, including severe obesity (BMI ≥ 40 kg/m²) and dyslipidemia (total cholesterol ≥200 mg/dL, non-high density lipoprotein [non-HDL] cholesterol ≥145 mg/dL or HDL cholesterol <40 mg/dL). We obtained mother’s age, education level, and parity as well as newborn sex, race, type of delivery, single/multiple birth, gestational age, and birthweight from birth certificate data. Individual-level socioeconomic status (SES) of the household at birth was determined with the HOUSES index.

Results:

Of 10 938 birth cohort subjects, 7394 had clinic visits after age 18 years and were included, with 2630 having severe obesity (n = 798) or dyslipidemia (n = 2357) as adults. In multivariable models, female sex, singleton birth, less maternal education, and lower SES defined by HOUSES were independently associated with an increased risk of severe obesity in adulthood. Non-white race, singleton birth, and lower birthweight were independently associated with adult dyslipidemia. Birthweight for gestational age was not associated with severe obesity or dyslipidemia.

Conclusion:

Perinatal factors were associated with both severe obesity and dyslipidemia in adulthood. Lower SES at birth was predictive of severe obesity in adulthood, highlighting the opportunity to investigate modifiable perinatal social determinants to reduce the risk of severe obesity.

Serum 25-hydroxyvitamin D values and risk of incident cardiovascular disease: A population-based retrospective cohort study

BACKGROUND

Concentrations of serum 25-hydroxyvitamin D [25(OH)D] below 20 ng/mL and above 50 ng/mL have been associated with chronic adverse events including cardiovascular disease.

OBJECTIVE

To conduct a comprehensive population-based study in the United States of the relationship of low and high serum 25(OH)D levels with cardiovascular disease.

METHODS

We identified all serum 25(OH)D measurements in adults age 18 years and older residing in Olmsted County, MN between January 1, 2005 and December 31, 2011, using the resources of the Rochester Epidemiology Project. Any new diagnosis of cardiovascular disease was the primary outcome, and time zero was 30 days after first 25(OH)D measurement. Patients were followed until their last clinical visit as an Olmsted County resident, December 31, 2014, or death. Categories of 25(OH)D values were examined using predetermined ranges of interest: <12, 12-19, 20-50 (reference range), and >50 ng/mL. Multivariable Cox proportional hazards models were adjusted for age, BMI, sex, race, smoking history, season of 25(OH)D measurement, hypertension, hyperlipidemia, socioeconomic status and Charlson comorbidity index at time of 25(OH)D measurement.

RESULTS

A total of 11,002 unique persons had a 25(OH)D measurement, with a mean (±SD) value of 30.0 ± 12.9 ng/mL. Mean age was 54.3 ± 17.2 years, and the majority were female (77.1 %) and white (87.6 %). There were 4124 new diagnoses of cardiovascular disease in this cohort after a median overall follow-up of 4.8 years (IQR 3.4-6.2). Adjusted cardiovascular disease hazard ratios (HRs) (95 % confidence interval) for 25(OH)D values <12, 12-19, and >50 ng/mL, compared to the reference range 20-50 ng/mL, were 1.28 (1.12-1.46), 1.19 (1.09-1.31), and 1.10 (0.95-1.26), respectively.

CONCLUSION

Values of 25(OH)D <20 ng/mL were associated with development of a new diagnosis of cardiovascular disease. There was no significant association between 25(OH)D values >50 ng/mL and cardiovascular disease.

Vitamin D Status and Severe COVID-19 Disease Outcomes in Hospitalized Patients

BACKGROUND

Vitamin D deficiency may increase the risk of severe COVID-19 disease.

OBJECTIVES

To determine if 25-hydroxyvitamin D [25(OH)D] levels in patients hospitalized for COVID-19 were associated with the clinical outcomes of days on oxygen, duration of hospitalization, ICU admission, need for assisted ventilation, or mortality.

METHODS

We conducted a retrospective study of 92 patients admitted to the hospital with SARS-CoV-2 infection between April 16, 2020 and October 17, 2020. Multivariable regression was performed to assess the independent relationship of 25(OH)D values on outcomes, adjusting for significant covariates and the hospitalization day the level was tested.

RESULTS

About 15 patients (16.3%) had 25(OH)D levels <20 ng/mL. Only 1 patient (3.4%) who had documented vitamin D supplementation prior to admission had 25(OH)D <20 ng/mL. Serum 25(OH)D concentrations were not significantly associated with any of our primary outcomes of days on oxygen, duration of hospitalization, intensive care unit (ICU) admission, need for mechanical ventilation, or mortality in any of the adjusted multivariable models. Adjusting for the hospital day of 25(OH)D sampling did not alter the relationship of 25(OH)D with any outcomes.

CONCLUSION

Vitamin D status was not related to any of the primary outcomes reflecting severity of COVID-19 in hospitalized patients. However, our sample size may have lacked sufficient power to demonstrate a small effect of vitamin D status on these outcomes.

The Validity of Serum Alkaline Phosphatase to Identify Nutritional Rickets in Nigerian Children on a Calcium-Deprived Diet

CONTEXT

Nutritional rickets results from the interaction of low vitamin D status and limited calcium intake. Serum alkaline phosphatase (AP) activity is a biomarker of impaired mineralization in rickets.

OBJECTIVE

To assess the performance of serum AP activity in identifying nutritional rickets in calcium-deprived Nigerian children.

METHODS

We reanalyzed data from a case-control study of children with active rickets and matched control subjects without rickets, using a multivariate logistic regression to assess the odds of rickets associated with AP activity, adjusting for age, sex, and weight-for-age z-score.

RESULTS

A total of 122 children with rickets and 119 controls were included. Rachitic children had a mean (±SD) age of 54 ± 29 months, and 55 (45.1%) were male. Cases and controls had low dietary calcium intakes (216 ± 87 and 214 ± 96 mg/day, respectively). Serum AP activity levels in cases and controls were 812 ± 415 and 245 ± 78 U/L, respectively (P < 0.001). AP was negatively associated with 25-hydroxyvitamin D values (r = -0.34; P < 0.001). In the adjusted model, the odds ratio (95% CI) receiver operating characteristic curve was 0.978. AP > 350 U/L identified nutritional rickets in Nigerian children with sensitivity 0.93, specificity 0.92, positive likelihood ratio 11.3, and negative likelihood ratio 0.07.

CONCLUSION

An AP > 350 U/L effectively discriminated between Nigerian children with and without nutritional rickets. AP is a low-cost biochemical test that could be used to screen for nutritional rickets, but cutoff values require validation in other populations, and laboratory values need to be standardized for widespread population studies.

Serum 25-Hydroxyvitamin D and Subsequent Cancer Incidence and Mortality: A Population-Based Retrospective Cohort Study

OBJECTIVE

To determine the relationship between 25-hydroxyvitamin D (25[OH]D) values and subsequent cancer incidence and mortality.

PATIENTS AND METHODS

We identified all adult patients living in Olmsted County, Minnesota, between January 1, 2005, and December 31, 2011, who had at least 1 25(OH)D measurement and no prior diagnosis of cancer. Cancer outcomes were retrieved starting 30 days after 25(OH)D measurement and until patients' final clinical visit as an Olmsted County resident; December 31, 2014; or death. Cox proportional hazards regression was used to analyze data.

RESULTS

A total of 8700 individuals had a 25(OH)D measurement and no history of cancer, with a mean ± SD 25(OH)D value of 29.7±12.8 ng/mL (to convert to nmol/L, multiply by 2.496). The mean ± SD age was 51.5±16.4 years, and most were women (78.1%; n=6796) and White (85.7%; n=7460). A total of 761 individuals developed cancer (skin cancer, n=360; nonskin cancer, n=401) during a median follow-up of 4.6 (interquartile range, 3.4-6.1) years. Compared with participants with 25(OH)D values of 20 to 50 ng/mL (reference group), those with 25(OH)D values less than 12 ng/mL had a greater nonskin cancer incidence (hazard ratio [HR], 1.56; 95% CI, 1.03 to 2.36; P=.04) after adjustment. There was no association between 25(OH)D values and total cancer or skin cancer incidence. Compared with individuals from the reference group, 25(OH)D levels less than 12 ng/mL (HR, 2.35; 95% CI, 1.01 to 5.48; P=.047) and 12 to 19 ng/mL (HR, 2.10; 95% CI, 1.05 to 4.22; P=.04) were associated with increased cancer mortality.

CONCLUSION

Low 25(OH)D levels were associated with increased risk for incident nonskin cancer and cancer-related mortality.

Validation of the Radiographic Global Impression of Change (RGI-C) score to assess healing of rickets in pediatric X-linked hypophosphatemia (XLH)

BACKGROUND

Rickets is a primary manifestation of pediatric X-linked hypophosphatemia (XLH) - a rare progressive hereditary phosphate-wasting disease. Severity is quantified from radiographs using the Rickets Severity Scale (RSS). The Radiographic Global Impression of Change (RGI-C) is a complementary assessment in which a change score is assigned based on differences in the appearance of rickets on pairs of radiographs compared side by side.

OBJECTIVE

The current study evaluated the reliability, validity, and sensitivity to change of the RGI-C specifically in pediatric XLH.

METHODS

The reliability, validity, and sensitivity to change of the RGI-C were evaluated using data from two studies in pediatric XLH (113 children aged 1-12 years) in which burosumab treatment significantly improved rickets severity. Intra-rater and inter-rater reliability were assessed by three pediatric radiologists.

RESULTS

Intra-rater reliability for RGI-C global score was >90% for agreement within 1 point, with weighted kappa values >0.5, indicating moderate to almost perfect agreement. Inter-rater reliability was also >90% (0.47-0.52 for all reader pairs; moderate agreement). The RGI-C global score showed significant relationships with changes from baseline to week 64 in serum phosphorus (r = -0.397), alkaline phosphatase (-0.611), total RSS (-0.672), standing height (0.268), and patient-reported global functioning (0.306) and comfort/pain functioning (0.409). Based on standardized response means, RGI-C global scores were sensitive to change in RSS, differentiating between those considered improved and greatly improved. Results for validity and sensitivity to change were similar for the RGI-C wrist, knee, and standing long leg scores.

CONCLUSION

The RGI-C is a reliable, valid, and sensitive measure in pediatric XLH, and complementary to the RSS.

Serum 25-hydroxyvitamin D requirements to prevent nutritional rickets in Nigerian children on a low-calcium diet-a multivariable reanalysis

BACKGROUND

Nutritional rickets is believed to result from the interaction of inadequate serum 25-hydroxyvitamin D [25(OH)D] concentration and dietary calcium intake, but this interaction has not been confirmed in children with rickets. Determining the vitamin D requirements to prevent nutritional rickets has been thwarted by inconsistent case definition, inadequate adjustment for calcium intake and other confounders, and 25(OH)D assay variability.

OBJECTIVES

To model the 25(OH)D concentration associated with nutritional rickets in calcium-deprived Nigerian children, adjusted for confounding factors, and develop a general approach to define vitamin D status while accounting for calcium intake.

METHODS

Logistic regression was used to model the association of serum 25(OH)D with having rickets adjusted for calcium intake in a reanalysis of a case-control study in Nigerian children. The matching variables age, sex, weight-for-age z score, and 4 additional significant variables were selected [religion, age began walking, phosphorus intake, and the 25(OH)D × calcium intake interaction] using a rigorous 7-step algorithm.

RESULTS

Cases had significantly (P < 0.0001) lower mean ± SD 25(OH)D than controls (33 ± 13 compared with 51 ± 16 nmol/L, respectively), whereas cases and controls had similarly (P = 0.81) low mean dietary calcium intakes (216 ± 88 and 213 ± 95 mg/d, respectively). There was a significant interaction between 25(OH)D and calcium intake [coefficient (95% CI): -0.0006 (-0.0009, -0.0002)]. Accordingly, as calcium intake increased from 130 to 300 mg/d, the adjusted odds of having rickets decreased dramatically with increasing 25(OH)D such that at 200 mg/d, the adjusted odds of having rickets at 47.5 nmol/L was 0.80, whereas it was 0.2 at 62.5 nmol/L. Moreover, at a calcium intake of 300 mg/d, the adjusted odds was 0.16 at a 25(OH)D concentration of 47.5 nmol/L and 0.02 at 62.5 nmol/L.

CONCLUSIONS

The vitamin D requirement to prevent nutritional rickets varies inversely with calcium intake and vice versa. Also, application of multivariable modeling is essential in defining vitamin D requirements.

Clinician Care Team Composition and Health Care Utilization

Objective

To test the hypothesis that a greater proportion of physician time on primary care teams are associated with decreased emergency department (ED) visits, hospital admissions, and readmissions, and to determine clinician and care team characteristics associated with greater utilization.

Patients and Methods

We retrospectively analyzed administrative data collected from January 1 to December 31, 2017, of 420 family medicine clinicians (253 physicians, 167 nurse practitioners/physician assistants [NP/PAs]) with patient panels in an integrated health system in 59 Midwestern communities serving rural and urban areas in Minnesota, Wisconsin, and Iowa. These clinicians cared for 419,581 patients through 110 care teams, with varying numbers of physicians and NP/PAs. Primary outcome measures were rates of ED visits, hospitalizations, and readmissions.

Results

The proportion of physician full-time equivalents on the team was unrelated to rates of ED visits (rate ratio [RR] = 0.826; 95% confidence interval [CI], 0.624 to 1.063), hospitalizations (RR = 0.894; 95% CI, 0.746 to 1.072), or readmissions (RR = –0.026; 95% CI, 0.364 to 0.312). In separate multivariable models adjusted for clinician and practice-level characteristics, the rate of ED visits was positively associated with mean panel hierarchical condition category (HCC) score, urban vs rural setting, NP/PA vs physician, and lower years in practice. The rate of inpatient admissions was associated with HCC score, and 30-day hospital readmissions were positively associated with HCC score, lower years in practice, and male clinicians.

Conclusion

Care team physician and NP/PA composition was not independently related to utilization. More complex panels had higher rates of ED visits, hospitalization, and readmissions. Statistically significant differences between physician and NP/PA panels were only evident for ED visits.

Relationship of Clinician Care Team Composition and Diabetes Quality Outcomes

The objective was to determine if a greater proportion of physician full-time equivalent (FTE%) relative to nurse practitioners/physician assistants (NPs/PAs) on care teams was associated with improved individual clinician diabetes quality outcomes. The authors conducted a retrospective cross-sectional study of 420 family medicine clinicians in 110 care teams in a Midwest health system, using administrative data from January 1, 2017 to December 31, 2017. Poisson regression was used to examine the relationship between physician FTE% and the number of patients meeting 5 criteria included in a composite metric for diabetes management (D5). Covariates included panel size, clinician type, sex, years in practice, region, patient satisfaction, care team size, rural location, and panel complexity. Of the 420 clinicians, 167 (40%) were NP/PA staff and 253 (60%) were physicians. D5 criteria were achieved in 37.9% of NP/PA panels compared with 44.5% of physician panels (P < .001). In adjusted analysis, rate of patients achieving D5 was unrelated to physician FTE% on the care team (P = .78). Physicians had a 1.082 (95% confidence interval 1.007-1.164) times greater rate of patients with diabetes achieving D5 than NPs/PAs. Clinicians at rural locations had a .904 (.852-.959) times lower rate of achieving D5 than those at urban locations. Physicians had a greater rate of patients achieving D5 compared with NPs/PAs, but physician FTE% on the care team was unrelated to D5 outcomes. This suggests that clinician team composition matters less than team roles and the dynamics of collaborative care between members.

The relationship of 25-hydroxyvitamin D values and risk of fracture: a population-based retrospective cohort study

Our study investigates 25-hydroxyvitamin D levels and fracture risk using population-level data. 25-Hydroxyvitamin D values < 12, 12-19, and > 50 ng/mL were not associated with increased risk of fractures overall compared with values 20-50 ng/mL. Severely low levels may be associated with increased risk of osteoporotic fracture, particularly of the wrist.

INTRODUCTION

Studies of the relationship between serum 25-hydroxyvitamin D (25(OH)D) levels and fracture risk have been inconsistent. We hypothesized that high 25(OH)D concentrations (> 50 ng/mL) would be associated with increased risk of fracture.

METHODS

We identified all adult patients living in Olmsted County, Minnesota, between January 1, 2005 and December 31, 2011, who had at least one 25(OH)D measurement. Fracture outcomes were retrieved starting 30 days after 25(OH)D measurement and until patients' final clinical visit as an Olmsted County resident, December 31, 2014, or death. Data were analyzed using Cox proportional hazard regression.

RESULTS

Of 11,002 individuals with a 25(OH)D measurement, 5.8% had a 25(OH)D value ˂ 12 ng/mL, and 5.1% had a value > 50 ng/mL. Compared with subjects with 25(OH)D values 20-50 ng/mL (reference group), values < 12, 12-19, and > 50 ng/mL displayed no association with overall fracture risk. After adjusting for a prior diagnosis of osteoporosis/osteopenia, only individuals with values ˂ 12 ng/mL had increased risk of any osteoporotic fracture (aHR = 1.41; 95% CI 1.05-1.89) and wrist fracture (aHR = 2.11; 95% CI 1.27-3.48) compared with the reference group. Compared with the reference group, values ˂ 12 ng/mL were associated with increased risk of any fracture (aHR = 1.35; 95% CI 1.01-1.80), osteoporotic fracture (aHR = 2.18; 95% CI 1.44-3.31), and wrist fracture (aHR = 2.39; 95% CI 1.19-4.81) in subjects without a prior diagnosis of osteoporosis/osteopenia, but not in those with a prior diagnosis of osteoporosis/osteopenia.

CONCLUSION

Severely low 25(OH)D levels may be associated with increased risk of osteoporotic fracture, particularly of the wrist, but 25(OH)D values > 50 ng/mL were not associated with increased fracture risk.

Association of Primary Care Team Composition and Clinician Burnout in a Primary Care Practice Network

Objective

To determine the relationship of the emotional exhaustion domain of burnout with care team composition in a Midwestern primary care practice network.

Participants and Methods

We studied 420 family medicine clinicians (253 physicians and 167 nurse practitioners/physician assistants [NP/PAs]) within a large integrated health system throughout 59 Midwestern communities. The observational cross-sectional study utilized a single-question clinician self-assessment of the emotional exhaustion domain of burnout on a scale of 0 (never) to 6 (daily) conducted between March 1 and April 2, 2018, and administrative data collected between January 1, 2017, and December 31, 2017. We used a multivariable linear mixed model for data analysis, adjusted for clinical- and team-level factors, including clinician sex, panel size and complexity, clinician type (physician or NP/PA), clinician full-time equivalent (FTE), total care team panel size, and number of clinicians on the care team.

Results

Among 217 survey respondents (51.7%), the median frequency of the emotional exhaustion domain of burnout was once per week. Adjusted analyses revealed that a greater proportion of physician FTE on the care team was associated with a lower emotional exhaustion domain of burnout among individual clinicians (P=.05). Female clinicians had a higher emotional exhaustion domain of burnout than male clinicians (P=.05). None of the other variables in the model were associated with emotional exhaustion.

Conclusion

Primary care teams containing both physicians and NP/PAs had lower levels of emotional exhaustion with increasing proportion of physician FTE. More work is needed to explore what other variables may be associated with burnout in primary care team-based practices.

The relationship of 25-hydroxyvitamin D concentrations and individual-level socioeconomic status

Socioeconomic status (SES), defined as the ability to access desired resources, is associated with behaviors that may affect vitamin D status. Most studies of the effect of vitamin D status on outcomes do not account for individual-level SES. The ability to adjust for SES in epidemiologic studies, when data on conventional SES measures have not been obtained, would be advantageous. We identified all serum 25(OH)D measurements in adults age 18 years and older residing in Olmsted County, MN, a mixed urban-rural setting, between January 1, 2005 and December 31, 2011, through the Rochester Epidemiology Project. The first 25(OH)D measurement was considered the index measurement for each subject. SES was determined for each subject by the HOUsing-based SocioEconomic Status (HOUSES) index, derived from real property data. The HOUSES index is an aggregated z-score of assessed housing value, area of living space, number of bedrooms, and number of bathrooms, with higher scores indicating higher SES. Multivariable analyses were adjusted for age, BMI, sex, race, season of 25(OH)D measurement, and Charlson comorbidity index. HOUSES was matched for 10,378 of 11,002 subjects (94 %) with 25(OH)D measurements available. The mean (SD) age was 54.3 (17.1) years with 26.9 % ≥65 years; 77.3 % were women, and 12.1 % were non-white. The mean 25(OH)D concentration was 30.0 (12.9) ng/mL, and 598 (5.8 %) had a 25(OH)D value <12 ng/mL. The mean (SD) HOUSES was -1.55 (3.09),-0.97 (3.34), 0.14 (3.52), 0.24 (3.51) for serum 25(OH)D categories of <12, 12-19, 20-50, and >50 ng/mL, respectively (P = 0.12 for trend). 25(OH)D increased by 0.43 (95 % CI 0.36-0.50) ng/mL for each unit increase in HOUSES in univariate analysis and by 0.28 (0.21-0.35; P < 0.001) ng/mL in multivariable analysis. This represents a change of 4 ng/mL across the entire range of observed HOUSES, an effect similar in magnitude to the seasonal variation of 25(OH)D values. SES was independently associated with serum 25(OH)D concentrations in a dose-response manner after adjustment for important covariates. HOUSES is a useful tool to assess the role of individual-level SES in health outcomes when other SES measures are unavailable and to control for confounding by SES in examining the effect of 25(OH)D on clinical and metabolic outcomes.

Population-Based Incidence of Potentially Life-Threatening Complications of Hypocalcemia and the Role of Vitamin D Deficiency

OBJECTIVES

To determine the incidence of potentially life-threatening complications of hypocalcemia in infants and children in Olmsted County, Minnesota; and to determine if vitamin D deficiency contributed to these events and was, at the time of clinical presentation, considered as a possible cause.

STUDY DESIGN

In this population-based descriptive study, data were abstracted from the Rochester Epidemiology Project, a medical record linkage system covering 95% of patients in Olmsted County, Minnesota. Participants were children aged 0-5 years who resided in Olmsted County between January 1, 1996 and June 30, 2017, and who received diagnoses of seizures, cardiomyopathy, cardiac arrest, respiratory arrest, laryngospasm, and/or tetany. The incidence of hypocalcemia plus a potentially life-threatening complication was calculated.

RESULTS

Among 15 419 patients aged 0-5 years in Olmsted County during the study period, 1305 had eligible complications: 460 had serum calcium checked within 14 days of presentation and 85 had hypocalcemia. Patients were excluded when causes other than hypocalcemia likely triggered the complication, leaving 16 children whose complication was attributed to hypocalcemia. Three of these 16 patients had a serum 25-hydroxyvitamin D measurement and 2 were deficient (≤6 ng/mL [15 nmol/L]). Among children aged 0-5 years, the incidence of hypocalcemia plus a potentially life-threatening complication was 6.1 per 100 000 person-years (95% CI, 3.5-10.0).

CONCLUSIONS

Vitamin D deficiency is an underinvestigated cause of complications of hypocalcemia in children. Serum calcium and 25-hydroxyvitamin D should be measured in children with these complications to identify possibly life-threatening vitamin D deficiency.

Rickets severity predicts clinical outcomes in children with X-linked hypophosphatemia: Utility of the radiographic Rickets Severity Score

The Rickets Severity Score (RSS) was used to evaluate X-linked hypophosphatemic rickets (XLH), a genetic disorder mediated by increased circulating FGF23. The reliability of the RSS was assessed using data from a randomized, phase 2 clinical trial that evaluated the effects of burosumab, a fully human anti-FGF23 monoclonal antibody, in 52 children with XLH ages 5 to 12 years. Bilateral knee and wrist radiographs were obtained at baseline, week 40, and week 64. We evaluated the relationships of the RSS to the Radiographic Global Impression of Change (RGI-C), serum alkaline phosphatase (ALP), height Z-score, 6-minute walk test (6MWT) percent predicted, and the Pediatric Orthopedic Society of North America Pediatric Outcomes Data Collection Instrument (POSNA-PODCI). The RSS showed moderate-to-substantial inter-rater reliability (weighted kappa, 0.45-0.65; Pearson correlation coefficient (r), 0.83-0.89) and substantial intra-rater reliability (weighted Kappa, 0.66; r = 0.91). Baseline RSS correlated with serum ALP (r = 0.47). Baseline RSS identified two subgroups (higher [RSS ≥1.5] and lower RSS [RSS <1.5]) that discriminated between subjects with greater and lesser rachitic disease. Higher RSS was associated with more severe clinical features, including impaired growth (Z-score, -2.12 vs -1.44) and walking ability (6MWT percent predicted, 77% vs 86%), more severe self-reported pain (29.9 [more severe] vs 45.3 [less severe]) and less physical function (29.6 [more severe] vs 40.9 [less severe]). During burosumab treatment, greater reductions in RSS corresponded to higher RGI-C global scores (r = -0.65). Improvements in RSS correlated with decreased serum ALP (r = 0.47). These results show the reliability of the RSS in XLH, and demonstrate that higher RSS values are associated with greater biochemical, clinical, and functional impairments in children with XLH.

Global prevalence and disease burden of vitamin D deficiency: a roadmap for action in low- and middle-income countries

Vitamin D is an essential nutrient for bone health and may influence the risks of respiratory illness, adverse pregnancy outcomes, and chronic diseases of adulthood. Because many countries have a relatively low supply of foods rich in vitamin D and inadequate exposure to natural ultraviolet B (UVB) radiation from sunlight, an important proportion of the global population is at risk of vitamin D deficiency. There is general agreement that the minimum serum/plasma 25-hydroxyvitamin D concentration (25(OH)D) that protects against vitamin D deficiency-related bone disease is approximately 30 nmol/L; therefore, this threshold is suitable to define vitamin D deficiency in population surveys. However, efforts to assess the vitamin D status of populations in low- and middle-income countries have been hampered by limited availability of population-representative 25(OH)D data, particularly among population subgroups most vulnerable to the skeletal and potential extraskeletal consequences of low vitamin D status, namely exclusively breastfed infants, children, adolescents, pregnant and lactating women, and the elderly. In the absence of 25(OH)D data, identification of communities that would benefit from public health interventions to improve vitamin D status may require proxy indicators of the population risk of vitamin D deficiency, such as the prevalence of rickets or metrics of usual UVB exposure. If a high prevalence of vitamin D deficiency is identified (>20% prevalence of 25(OH)D < 30 nmol/L) or the risk for vitamin D deficiency is determined to be high based on proxy indicators (e.g., prevalence of rickets >1%), food fortification and/or targeted vitamin D supplementation policies can be implemented to reduce the burden of vitamin D deficiency-related conditions in vulnerable populations.

Cardiac, bone and growth plate manifestations in hypocalcemic infants: revealing the hidden body of the vitamin D deficiency iceberg

BACKGROUND

Whilst hypocalcemic complications from vitamin D deficiency are considered rare in high-income countries, they are highly prevalent among Black, Asian and Minority Ethnic (BAME) group with darker skin. To date, the extent of osteomalacia in such infants and their family members is unknown. Our aim was to investigate clinical, cardiac and bone histomorphometric characteristics, bone matrix mineralization in affected infants and to test family members for biochemical evidence of osteomalacia.

CASE PRESENTATION

Three infants of BAME origin (aged 5-6 months) presented acutely in early-spring with cardiac arrest, respiratory arrest following seizure or severe respiratory distress, with profound hypocalcemia (serum calcium 1.22-1.96 mmol/L). All infants had dark skin and vitamin D supplementation had not been addressed during child surveillance visits. All three had severely dilated left ventricles (z-scores + 4.6 to + 6.5) with reduced ejection fraction (25-30%; normal 55-70), fractional shortening (7 to 15%; normal 29-40) and global hypokinesia, confirming hypocalcemic dilated cardiomyopathy. They all had low serum levels of 25 hydroxyvitamin D (25OHD < 15 nmol/L), and elevated parathyroid hormone (PTH; 219-482 ng/L) and alkaline phosphatase (ALP; 802-1123 IU/L), with undiagnosed rickets on radiographs. One infant died from cardiac arrest. At post-mortem examination, his growth plate showed a widened, irregular zone of hypertrophic chondrocytes. Histomorphometry and backscattered electron microscopy of a trans-iliac bone biopsy sample revealed increased osteoid thickness (+ 262% of normal) and osteoid volume/bone volume (+ 1573%), and extremely low bone mineralization density. Five of the nine tested family members had vitamin D deficiency (25OHD < 30 nmol/L), three had insufficiency (< 50 nmol/L) and 6/9 members had elevated PTH and ALP levels.

CONCLUSIONS

The severe, hidden, cardiac and bone pathology described here exposes a failure of public health prevention programs, as complications from vitamin D deficiency are entirely preventable by routine supplementation. The family investigations demonstrate widespread deficiency and undiagnosed osteomalacia in ethnic risk groups and call for protective legislation.

Serum 25-Hydroxyvitamin D Values and Risk of All-Cause and Cause-Specific Mortality: A Population-Based Cohort Study

OBJECTIVE

To determine the relationship between 25-hydroxyvitamin D (25[OH]D) values and all-cause and cause-specific mortality.

PATIENTS AND METHODS

We identified all serum 25(OH)D measurements in adults residing in Olmsted County, Minnesota, between January 1, 2005, and December 31, 2011, through the Rochester Epidemiology Project. All-cause mortality was the primary outcome. Patients were followed up until their last clinical visit as an Olmsted County resident, December 31, 2014, or death. Multivariate analyses were adjusted for age, sex, race/ethnicity, month of measurement, and Charlson comorbidity index score.

RESULTS

A total of 11,022 individuals had a 25(OH)D measurement between January 1, 2005, and December 31, 2011, with a mean ± SD value of 30.0±12.9 ng/mL. Mean age was 54.3±17.2 years, and most were female (77.1%) and white (87.6%). There were 723 deaths after a median follow-up of 4.8 years (interquartile range, 3.4-6.2 years). Unadjusted all-cause mortality hazard ratios (HRs) and 95% CIs for 25(OH)D values of less than 12, 12 to 19, and more than 50 ng/mL were 2.6 (95% CI, 2.0-3.2), 1.3 (95% CI, 1.0-1.6), and 1.0 (95% CI, 0.72-1.5), respectively, compared with the reference value of 20 to 50 ng/mL. In a multivariate model, the interaction between the effect of 25(OH)D and race/ethnicity on mortality was significant (P<.001). In white patients, adjusted HRs for 25(OH)D values of less than 12, 12 to 19, 20 to 50, and greater than 50 ng/mL were 2.5 (95% CI, 2.2-2.9), 1.4 (95% CI, 1.2-1.6), 1.0 (referent), and 1.0 (95% CI, 0.81-1.3), respectively. In patients of other race/ethnicity, adjusted HRs were 1.9 (95% CI, 1.5-2.3), 1.7 (95% CI, 1.1-2.6), 1.5 (95% CI, 1.0-2.0), and 2.1 (95% CI, 0.77-5.5).

CONCLUSION

White patients with 25(OH)D values of less than 20 ng/mL had greater all-cause mortality than those with values of 20 to 50 ng/mL, and white patients had greater mortality associated with low 25(OH)D values than patients of other race/ethnicity. Values of 25(OH)D greater than 50 ng/mL were not associated with all-cause mortality.

The relationship between maternal and child bone density in Nigerian children with and without nutritional rickets

We found a positive relationship between bone density in Nigerian children with and without rickets and that of their mothers. After treatment, children with rickets had greater bone density than children without rickets, indicating that children genetically programmed to have greater bone density may have a higher risk of rickets.

INTRODUCTION

To determine the relationship between bone density in children with and without rickets and that of their mothers METHODS: Using an unmatched case-control design, forearm areal bone mineral density (aBMD) was measured in 52 and 135 Nigerian children with and without rickets and their mothers, respectively. We performed multivariate linear regression analyses to assess the relationship between maternal and child aBMD Z-scores.

RESULTS

Forearm aBMD Z-scores in children were associated with maternal aBMD Z-scores at metaphyseal (effect estimate 0.23; 95% CI 0.08 to 0.37) and diaphyseal (effect estimate 0.16; 0.01 to 0.30) sites, after adjustment for rickets in the child, child's age and sex, height-for-age Z-score, and weight-for-age Z-score. In the adjusted model, rickets was inversely associated with child's aBMD Z-score at the diaphyseal site only (- 0.45, - 0.65 to - 0.24). The positive relationship between maternal and child aBMD Z-scores was marginally greater in children with rickets (slope 0.56, r = 0.47) than without rickets (slope 0.19, r = 0.20) at the diaphyseal site only (P = 0.06 for interaction) but not at the metaphyseal site (slopes 0.35 and 0.30, respectively, P = 0.48). After treatment with calcium for 6 months, metaphyseal aBMD Z-scores were greater in children with treated rickets (effect estimate 0.26; 95% CI 0.02 to 0.49) than in those without rickets.

CONCLUSION

In Nigerian children with and without rickets, forearm aBMD Z-scores were positively associated with maternal aBMD Z-scores. Active rickets in the child marginally modified the relationship at the diaphyseal site only. After treatment, children with rickets had greater metaphyseal aBMD Z-scores than children without rickets.

Comparison of the effect of daily versus bolus dose maternal vitamin D3 supplementation on the 24,25-dihydroxyvitamin D3 to 25-hydroxyvitamin D3 ratio

OBJECTIVE

Supplementing lactating mothers with high doses of vitamin D₃ can adequately meet vitamin D requirements of the breastfed infant. We compared the effect of bolus versus daily vitamin D₃ dosing in lactating mothers on vitamin D₃ catabolism. We hypothesized that catabolism of 25(OH)D₃ to 24,25(OH)₂D₃ would be greater in the bolus than in the daily dose group.

DESIGN, SETTING AND PATIENTS

Randomized controlled trial (clinicaltrials.govNCT01240265) in 40 lactating women.

INTERVENTIONS

Subjects were randomized to receive vitamin D₃ orally, either a single dose of 150,000IU or 5000IU daily for 28days. Vitamin D metabolites were measured in serum and breast milk at baseline, 1, 3, 7, 14 and 28days.

MAIN OUTCOME MEASURE

Temporal changes in the serum 24,25(OH)₂D₃/25(OH)D₃ ratio.

RESULTS

The concentration of serum 24,25(OH)₂D₃ was directly related to that of 25(OH)D in both groups (r²=0.63; p<0.001). The mean (±SD) 24,25(OH)₂D₃/25(OH)D₃ ratio remained lower at all time points than baseline values in the daily dose group (0.093±0.024, 0.084±0.025, 0.083±0.024, 0.080±0.020, 0.081±0.023, 0.083±0.018 at baseline, 1, 3, 7, 14, and 28days, respectively). In the single dose group, the increase in 24,25(OH)₂D₃ lagged behind that of 25(OH)D, but the 24,25(OH)₂D₃/25(OH)D₃ values (0.098±0.032, 0.067±0.019, 0.081±0.017, 0.092±0.024, 0.103±0.020, 0.106±0.024, respectively) exceeded baseline values at 14 and 28days and were greater than the daily dose group at 14 and 28days (p=0.003). The 24,25(OH)₂D₃/25(OH)D₃ ratio remained in the normal range with both dosing regimens. Greater breast milk vitamin D₃ values in the single dose group were inversely associated with the 24,25(OH)₂D₃/25(OH)D₃ ratio (r²=0.14, p<0.001), but not with daily dosing.

CONCLUSIONS

After a 14-day lag, a single high dose of vitamin D led to greater production of 24,25(OH)₂D₃, presumably via induction of the 24-hydroxylase enzyme (CYP24A1), relative to the 25(OH)D₃ value than did daily vitamin D supplementation, and this effect persisted for at least 28days after vitamin D administration. A daily dose of vitamin D may have more lasting effectiveness in increasing 25(OH)D₃ with lesser diversion of 25(OH)D₃ to 24,25(OH)₂D₃ than does larger bolus dosing.

CYP3A4 mutation causes vitamin D-dependent rickets type 3

Genetic forms of vitamin D-dependent rickets (VDDRs) are due to mutations impairing activation of vitamin D or decreasing vitamin D receptor responsiveness. Here we describe two unrelated patients with early-onset rickets, reduced serum levels of the vitamin D metabolites 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, and deficient responsiveness to parent and activated forms of vitamin D. Neither patient had a mutation in any genes known to cause VDDR; however, using whole exome sequencing analysis, we identified a recurrent de novo missense mutation, c.902T>C (p.I301T), in CYP3A4 in both subjects that alters the conformation of substrate recognition site 4 (SRS-4). In vitro, the mutant CYP3A4 oxidized 1,25-dihydroxyvitamin D with 10-fold greater activity than WT CYP3A4 and 2-fold greater activity than CYP24A1, the principal inactivator of vitamin D metabolites. As CYP3A4 mutations have not previously been linked to rickets, these findings provide insight into vitamin D metabolism and demonstrate that accelerated inactivation of vitamin D metabolites represents a mechanism for vitamin D deficiency.

Vitamin D and the Breastfeeding Infant: Family Medicine Clinicians' Knowledge, Attitudes, and Practices

BACKGROUND

The American Academy of Pediatrics and the National Academy of Medicine recommend vitamin D supplementation for breastfeeding infants. However, compliance with this recommendation is poor. Maternal supplementation with vitamin D is a safe and effective alternative to achieving vitamin D sufficiency in breastfeeding infants, and mothers have indicated a preference for self-supplementation over infant supplementation. Research aim: We sought to explore Family Medicine clinicians' knowledge, attitudes, and practices regarding vitamin D supplementation recommendations for breastfeeding dyads.

METHODS

Fifty-six Family Medicine clinicians (including faculty physicians, resident physicians, and nurse practitioners/physician assistants) completed an online, anonymous survey regarding their knowledge and practices concerning vitamin D supplementation for breastfeeding infants.

RESULTS

The vast majority of clinicians (92.9%) correctly identified the American Academy of Pediatrics' 2008 recommended dose for vitamin D supplementation in breastfeeding infants and estimated recommending vitamin D supplementation of exclusively breastfeeding infants 70.1% of the time. If all options were equivalent, clinicians would prefer to offer maternal or infant supplementation (50%) or maternal supplementation (37.5%) over infant supplementation (12.5%). Most (69.6%) preferred daily over monthly supplementation regimens.

CONCLUSION

Family Medicine clinicians are knowledgeable regarding current recommendations for vitamin D supplementation in breastfeeding infants. They are also open to recommending maternal supplementation or offering parents a choice of maternal or infant vitamin supplementation.

CYP2R1 mutations causing vitamin D-deficiency rickets

CYP2R1 is the principal hepatic 25-hydroxylase responsible for the hydroxylation of parent vitamin D to 25-hydroxyvitamin D [25(OH)D]. Serum concentrations of 25(OH)D reflect vitamin D status, because 25(OH)D is the major circulating metabolite of vitamin D. The 1α-hydroxylation of 25(OH)D in the kidney by CYP27B1 generates the fully active vitamin D metabolite, 1,25-dihydroxyvitamin D (1,25(OH)₂D). The human CYP2R1 gene, located at 11p15.2, has five exons, coding for an enzyme with 501 amino acids. In Cyp2r1-/- knockout mice, serum 25(OH)D levels were reduced by more than 50% compared wild-type mice. Genetic polymorphisms of CYP2R1 account for some of the individual variability of circulating 25(OH)D values in the population. We review the evidence that inactivating mutations in CYP2R1 can lead to a novel form of vitamin D-deficiency rickets resulting from impaired 25-hydroxylation of vitamin D. We sequenced the promoter, exons and intron-exon flanking regions of the CYP2R1 gene in members of 12 Nigerian families with rickets in more than one family member. We found missense mutations (L99P and K242N) in affected members of 2 of 12 families. The L99P mutation had previously been reported as a homozygous defect in an unrelated child of Nigerian origin with rickets. In silico analyses predicted impaired CYP2R1 folding or reduced interaction with substrate vitamin D by L99P and K242N mutations, respectively. In vitro studies of the mutant CYP2R1 proteins in HEK293 cells confirmed normal expression levels but completely absent or markedly reduced 25-hydroxylase activity by the L99P and K242N mutations, respectively. Heterozygous subjects had more moderate biochemical and clinical features of vitamin D deficiency than homozygous subjects. After an oral bolus dose of 50,000 IU of vitamin D₂ or vitamin D₃, heterozygous subjects had lower increases in serum 25(OH)D than control subjects, and homozygous subjects had minimal increases, supporting a semidominant inheritance of these mutations. No CYP2R1 mutations were found in 27 Nigerian children with sporadic rickets, a cohort of 50 unrelated Nigerian subjects, or in 628 unrelated subjects in the 1000 Genomes Project. We conclude that mutations in CYP2R1 are responsible for an atypical form of vitamin D-deficiency rickets, which has been classified as vitamin D dependent rickets type 1B (VDDR1B, MIM 600081).

Nutritional rickets around the world: an update

Worldwide, nutritional rickets continues to be an evolving problem with several causes. This paper provides an updated literature review characterising the prevalence, aetiology, pathophysiology and treatment of nutritional rickets worldwide. A systematic review of articles on nutritional rickets from various geographical regions was undertaken. For each region, key information was extracted, including prevalence, cause of rickets specific to the region, methods of confirming the diagnosis and current treatment and preventive measures. Calcium deficiency continues to be a major cause of rickets in Africa and Asia. Vitamin D deficiency rickets is perhaps increasing in the Americas, Europe and parts of the Middle East. There continues to be a distinct presentation of calcium-predominant versus vitamin D predominant rickets, although there are overlapping features. More careful diagnosis of rickets and reporting of 25-OHD concentrations has improved accurate knowledge of rickets prevalence and better delineated the cause. Nutritional rickets continues to be an evolving and multi-factorial problem worldwide. It is on a spectrum, ranging from isolated vitamin D deficiency to isolated calcium deficiency. Specific areas which require emphasis include a consistent community approach to screening and diagnosis, vitamin D supplementation of infants and at-risk children, prevention of maternal vitamin D deficiency and the provision of calcium in areas with low calcium diets.

The relationship of maternal bone density with nutritional rickets in Nigerian children

Factors that affect maternal bone mineral density may be related to the risk of nutritional rickets in their offspring. Our aim was to determine the relationship between maternal areal bone mineral density (aBMD) and rickets in Nigerian children. Using a case-control design, we measured forearm aBMD in 56 and 135 mothers of children with and without nutritional rickets, respectively. Active rickets was confirmed or excluded in all children radiographically. Using logistic regression, we assessed the association of maternal aBMD, adjusted for parity, pregnancy and lactation status, duration of most recent completed lactation, age of menarche, height, body mass index, and maternal age with nutritional rickets. The median (range) age of all mothers was 30years (17-47years), and parity was 4 (1-12). A total of 36 (19%) were pregnant and 55 (29%) were currently breast feeding. Mean (±SD) metaphyseal forearm aBMDs were 0.321±0.057 and 0.316±0.053g/cm² in mothers of children with and without rickets, respectively (P=0.60). Diaphyseal forearm aBMDs were 0.719±0.071 and 0.715±0.072g/cm², respectively (P=0.69). In an adjusted analysis, maternal forearm aBMD, bone mineral content and bone area at metaphyseal and diaphyseal sites were not associated with rickets in the child. In the adjusted analysis, rickets was associated with shorter duration of most recently completed lactation (aOR 0.91 for each additional month; 95% CI 0.83-0.99), older maternal age (aOR 1.07 for each additional year; 1.00-1.14), and less frequent maternal use of lead-containing eye cosmetics (aOR 0.20; 95% CI 0.05-0.64), without any difference in maternal blood lead levels. Maternal age, parity, age of menarche, height, and body mass index were not associated with having had a child with rickets in multivariate analysis. Nutritional rickets in Nigerian children was not associated with maternal forearm aBMD. Other unidentified maternal characteristics and practices likely contribute to the risk of rickets in Nigerian children.

Maternal Preferences for Vitamin D Supplementation in Breastfed Infants

Daily vitamin D supplementation is recommended for breastfed infants, but alternative methods include enriching breast milk with vitamin D through maternal supplementation or intermittent high-dose vitamin D. We determined maternal preferences for vitamin D supplementation in 140 mothers with exclusively breastfed infants, and 44 who used both breast and formula milk. Only 101 (55%) supplemented their infants with vitamin D. One hundred sixty (88%) preferred supplementing themselves rather than their infants, and 102 (57%) preferred daily to monthly supplementation. Safety was most important in choosing a method of supplementation. Taking maternal preferences into consideration may improve adequate intakes of vitamin D in breastfed infants.

Global Consensus Recommendations on Prevention and Management of Nutritional Rickets

BACKGROUND

Vitamin D and calcium deficiencies are common worldwide, causing nutritional rickets and osteomalacia, which have a major impact on health, growth, and development of infants, children, and adolescents; the consequences can be lethal or can last into adulthood. The goals of this evidence-based consensus document are to provide health care professionals with guidance for prevention, diagnosis, and management of nutritional rickets and to provide policy makers with a framework to work toward its eradication.

EVIDENCE

A systematic literature search examining the definition, diagnosis, treatment, and prevention of nutritional rickets in children was conducted. Evidence-based recommendations were developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system that describes the strength of the recommendation and the quality of supporting evidence.

PROCESS

Thirty-three nominated experts in pediatric endocrinology, pediatrics, nutrition, epidemiology, public health, and health economics evaluated the evidence on specific questions within five working groups. The consensus group, representing 11 international scientific organizations, participated in a multiday conference in May 2014 to reach a global evidence-based consensus.

RESULTS

This consensus document defines nutritional rickets and its diagnostic criteria and describes the clinical management of rickets and osteomalacia. Risk factors, particularly in mothers and infants, are ranked, and specific prevention recommendations including food fortification and supplementation are offered for both the clinical and public health contexts.

CONCLUSION

Rickets, osteomalacia, and vitamin D and calcium deficiencies are preventable global public health problems in infants, children, and adolescents. Implementation of international rickets prevention programs, including supplementation and food fortification, is urgently required.

Optimal Dose of Calcium for Treatment of Nutritional Rickets: A Randomized Controlled Trial

Calcium supplementation is indicated for the treatment of nutritional rickets. Our aim was to determine the optimal dose of calcium for treatment of children with rickets. Sixty-five Nigerian children with radiographically confirmed rickets were randomized to daily supplemental calcium intake of 500 mg (n = 21), 1000 mg (n = 23), or 2000 mg (n = 21). Venous blood, radiographs, and forearm areal bone density (aBMD) were obtained at baseline and at 8, 16, and 24 weeks after enrollment. The primary outcome was radiographic healing, using a 10-point radiographic severity score. The radiographic severity scores improved in all three groups, but the rate of radiographic healing (points per month) was significantly more rapid in the 1000-mg (-0.29; 95% confidence interval [CI] -0.13 to -0.45) and 2000-mg (-0.36; 95% CI -0.19 to -0.53) supplementation groups relative to the 500-mg group. The 2000-mg group did not heal more rapidly than the 1000-mg group. Of those who completed treatment for 24 weeks, 12 (67%), 20 (87%), and 14 (67%) in the 2000-mg, 1000-mg, and 500-mg groups, respectively, had achieved a radiographic score of 1.5 or less (p = 0.21). Serum alkaline phosphatase decreased and calcium increased similarly in all groups. Forearm diaphyseal aBMD improved significantly more rapidly in the 2000-mg group than in the 500-mg and 1000-mg groups (p < 0.001). Daily calcium intakes of 1000 mg or 2000 mg produced more rapid radiographic healing of rickets than 500 mg, but 2000 mg did not have greater benefit than 1000 mg. Some children require longer than 24 weeks for complete healing of nutritional rickets. © 2016 American Society for Bone and Mineral Research.

Nutritional rickets in immigrant and refugee children

Immigrant and refugee populations bring public health challenges to host nations. In the current global refugee crisis, children are the most vulnerable subpopulation. Diseases that were considered rare in the host nation may be highly prevalent among immigrant children. The prevalence of nutritional rickets is increasing in high-income countries, largely driven by an influx of immigrant populations. Nutritional rickets is a bone disease in early childhood resulting in bone pain, delayed motor development, and bending of the bones, caused by vitamin D deficiency and/or inadequate dietary calcium intake. The consequences of nutritional rickets include stunted growth, developmental delay, lifelong bone deformities, seizures, cardiomyopathy, and even death. Nutritional rickets is most commonly seen in children from the Middle East, Africa, and South Asia in high-income countries. Dark skin pigmentation, sun avoidance, covering the skin, and prolonged breast feeding without vitamin D supplementation, are important risk factors for vitamin D deficiency, and combined with a lack of dairy products in the diet, these deficiencies can result in insufficient calcium supply for bone mineralization. We recommend screening all immigrant and refugee children under 5 years of age from these ethnic groups for nutritional rickets, based on clinical features, and confirming the diagnosis with radiographs of the wrists and knees. Because nutritional rickets is entirely preventable, public health policies must address the need for universal vitamin D supplementation and adequate dietary calcium to protect children from this scourge. Vitamin D supplementation of all infants and children with 400 IU/d during the first year of life and dietary or supplemental intakes of at least 600 IU/d of vitamin D and 500 mg/d of calcium thereafter, will effectively prevent nutritional rickets. We call on national health authorities of host countries to implement health check lists and prevention programs that include screening for micronutrient deficiencies, in addition to assessing infections and vaccination programs. Due to their high prevalence of vitamin D deficiency, refugee children of all ages from these ethnic groups should be supplemented with vitamin D, beginning upon arrival.

Global Consensus Recommendations on Prevention and Management of Nutritional Rickets

BACKGROUND

Vitamin D and calcium deficiencies are common worldwide, causing nutritional rickets and osteomalacia, which have a major impact on health, growth, and development of infants, children, and adolescents; the consequences can be lethal or can last into adulthood. The goals of this evidence-based consensus document are to provide health care professionals with guidance for prevention, diagnosis, and management of nutritional rickets and to provide policy makers with a framework to work toward its eradication.

EVIDENCE

A systematic literature search examining the definition, diagnosis, treatment, and prevention of nutritional rickets in children was conducted. Evidence-based recommendations were developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system that describe the strength of the recommendation and the quality of supporting evidence.

PROCESS

Thirty-three nominated experts in pediatric endocrinology, pediatrics, nutrition, epidemiology, public health, and health economics evaluated the evidence on specific questions within five working groups. The consensus group, representing 11 international scientific organizations, participated in a multiday conference in May 2014 to reach a global evidence-based consensus.

RESULTS

This consensus document defines nutritional rickets and its diagnostic criteria and describes the clinical management of rickets and osteomalacia. Risk factors, particularly in mothers and infants, are ranked, and specific prevention recommendations including food fortification and supplementation are offered for both the clinical and public health contexts.

CONCLUSION

Rickets, osteomalacia, and vitamin D and calcium deficiencies are preventable global public health problems in infants, children, and adolescents. Implementation of international rickets prevention programs, including supplementation and food fortification, is urgently required.

CYP2R1 Mutations Impair Generation of 25-hydroxyvitamin D and Cause an Atypical Form of Vitamin D Deficiency

CONTEXT

Production of the active vitamin D hormone 1,25-dihydroxyvitamin D requires hepatic 25-hydroxylation of vitamin D. The CYP2R1 gene encodes the principal vitamin D 25-hydroxylase in humans.

OBJECTIVE

This study aimed to determine the prevalence of CYP2R1 mutations in Nigerian children with familial rickets and vitamin D deficiency and assess the functional effect on 25-hydroxylase activity.

DESIGN AND PARTICIPANTS

We sequenced the CYP2R1 gene in subjects with sporadic rickets and affected subjects from families in which more than one member had rickets.

MAIN OUTCOME MEASURES

Function of mutant CYP2R1 genes as assessed in vivo by serum 25-hydroxyvitamin D values after administration of vitamin D and in vitro by analysis of mutant forms of the CYP2R1.

RESULTS

CYP2R1 sequences were normal in 27 children with sporadic rickets, but missense mutations were identified in affected members of 2 of 12 families, a previously identified L99P, and a novel K242N. In silico analyses predicted that both substitutions would have deleterious effects on the variant proteins, and in vitro studies showed that K242N and L99P had markedly reduced or complete loss of 25-hydroxylase activity, respectively. Heterozygous subjects were less affected than homozygous subjects, and oral administration of vitamin D led to significantly lower increases in serum 25-hydroxyvitamin D in heterozygous than in control subjects, whereas homozygous subjects showed negligible increases.

CONCLUSION

These studies confirm that CYP2R1 is the principal 25-hydroxylase in humans and demonstrate that CYP2R1 alleles have dosage-dependent effects on vitamin D homeostasis. CYP2R1 mutations cause a novel form of genetic vitamin D deficiency with semidominant inheritance.

Comparison of Limestone and Ground Fish for Treatment of Nutritional Rickets in Children in Nigeria

OBJECTIVE

To determine whether children with calcium-deficiency rickets respond better to treatment with calcium as limestone or as ground fish.

STUDY DESIGN

Nigerian children with active rickets (n = 96) were randomized to receive calcium as powdered limestone (920 mg of elemental calcium) or ground fish (952 mg of elemental calcium) daily for 24 weeks. Radiographic healing was defined as achieving a score of 1.5 or less on a 10-point scale.

RESULTS

The median (range) age of enrolled children was 35 (6-151) months. Of the 88 children who completed the study, 29 (66%) in the ground fish group and 24 (55%) in the limestone group achieved the primary outcome of a radiographic score of 1.5 or less within 6 months (P = .39). The mean radiographic score improved from 6.2 ± 2.4 to 1.8 ± 2.2 in the ground fish group and from 6.3 ± 2.2 to 2.1 ± 2.4 in the limestone group (P = .68 for group comparison). In an intention to treat analysis adjusted for baseline radiographic score, age, milk calcium intake, and serum 25-hydroxyvitamin D concentration, the response to treatment did not differ between the 2 groups (P = .39). Younger age was associated with more complete radiographic healing in the adjusted model (aOR 0.74 [95% CI 0.57-0.92]). After 24 weeks of treatment, serum alkaline phosphatase had decreased, calcium and 25-hydroxyvitamin D increased, and bone mineral density increased in both groups, without significant differences between treatment groups.

CONCLUSION

In children with calcium-deficiency rickets, treatment with calcium as either ground fish or limestone for 6 months healed rickets in the majority of children.

Changing Incidence of Serum 25-Hydroxyvitamin D Values Above 50 ng/mL: A 10-Year Population-Based Study

OBJECTIVE

To determine the incidence trend of 25-hydroxyvitamin D (25(OH)D) values above 50 ng/mL and associated toxicity.

PATIENTS AND METHODS

We conducted a retrospective population-based study in Olmsted County, Minnesota, in the 10-year period from January 1, 2002, through December 31, 2011, by using the Rochester Epidemiology Project. Individuals were eligible if they resided in Olmsted County during the study period and had a measured 25(OH)D value above 50 ng/mL. The date of the first 25(OH)D value above 50 ng/mL was considered the index date for incidence determination. Hypercalcemia, the primary vitamin D toxicity, was considered potentially associated with the 25(OH)D concentration if it was measured within 3 months of the 25(OH)D measurement, and such cases had a medical record review.

RESULTS

Of 20,308 total 25(OH)D measurements, 1714 (8.4%), 123 (0.6%), and 37 (0.2%) unique persons had 25(OH)D values above 50, 80 and above, and 100 ng/mL and above, respectively. The age- and sex-adjusted incidence of 25(OH)D values above 50 ng/mL increased from 9 to 233 cases per 100,000 person-years from 2002 to 2011 (P<.001), respectively, and was greatest in persons aged 65 years and older (P<.001) and in women (P<.001). Serum 25(OH)D values were not significantly related to serum calcium values (P=.20) or with the risk of hypercalcemia (P=.24). A medical record review identified 4 cases (0.2%) in whom 25(OH)D values above 50 ng/mL were temporally associated with hypercalcemia, but only 1 case had clinical toxicity associated with the highest observed 25(OH)D value of 364 ng/mL.

CONCLUSION

The incidence of 25(OH)D values above 50 ng/mL increased significantly between 2002 and 2011 without a corresponding increase in acute clinical toxicity.

US Preventative Services Task Force FRAX threshold has a low sensitivity to detect osteoporosis in women ages 50-64 years

The US Preventative Services Task Force (USPSTF) recommends consideration for screening for osteoporosis in women under age 65 who have an estimated 10-year major osteoporotic fracture risk of 9.3 % or higher. We found that this threshold for osteoporosis screening in women ages 50-64 years old has a low sensitivity to detect osteoporosis.

INTRODUCTION

The US Preventative Services Task Force (USPSTF) recommends consideration of dual-energy X-ray absorptiometry (DXA) in women under ages 50-64 with a major osteoporotic fracture (MOF) risk of 9.3 % or higher, as estimated by the fracture risk assessment tool (FRAX) tool. We assessed the performance of the 9.3 % MOF risk threshold for detecting osteoporosis and evaluated whether DXA indication appeared appropriate, based on USPSTF criteria and other risk factors, at our institution.

METHODS

We performed a retrospective record review of women ages 50-64.5 years old to determine clinical factors and FRAX scores of women undergoing a DXA at our institution over a 6-month period after the USPSTF recommendations were released and evaluated the sensitivity and specificity of the 9.3 % MOF threshold to detect densitometric osteoporosis. Additionally, using the USPSTF criteria and several additional risk factors, we evaluated the extent of potentially inappropriate DXA use in women ages 50 to 64 years in a large primary care practice in an academic medical center.

RESULTS

The analysis included 465 DXA tests. The overall sensitivity and specificity of a FRAX-calculated MOF risk ≥9.3 % was 37 and 74 %, respectively, for the detection of osteoporosis. The receiver operator characteristic curve (ROC) demonstrated an area under the curve of 0.58. Lowering the FRAX risk threshold to 5.5 % would increase the sensitivity of detecting osteoporosis in our population from 37 to 80 % while reducing the specificity from 74 to 27 %. Out of 465 DXAs, 371 (79.8 %) were classified as appropriately ordered per our pre-specified criteria. Of the 120 women with osteoporosis at the hip and/or spine based on T-score values of -2.5 or less, 14 DXAs (11.7 %) were classified as potentially inappropriate based on a FRAX-predicted MOF risk less than 9.3 % and lack of additional pre-specified risk factors.

CONCLUSION

We found that the USPSTF-recommended MOF risk threshold of 9.3 % for osteoporosis screening in women ages 50-64 years old has a low sensitivity to detect osteoporosis.

Predictors of malaria in febrile children in Sokoto, Nigeria

Background:

Presumptive diagnosis of malaria is widespread, even where microscopy is available. As fever is very nonspecific, this often leads to over diagnosis, drug wastage and loss of opportunity to consider alternative causes of fever, hence the need to improve on the clinical diagnosis of malaria.

Materials and Methods:

In a prospective cross-sectional comparative study, we examined 45 potential predictors of uncomplicated malaria in 800 febrile children (0-12 years) in Sokoto, Nigeria. We developed a clinical algorithm for malaria diagnosis and compared it with a validated algorithm, Olaleye's model.

Results:

Malaria was confirmed in 445 (56%). In univariate analysis, 13 clinical variables were associated with malaria. In multivariate analysis, vomiting (odds ratio, OR 2.6), temperature ≥ 38.5°C (OR 2.2), myalgia (OR 1.8), weakness (OR 1.9), throat pain (OR 1.8) and absence of lung crepitations (OR 5.6) were independently associated with malaria. In children over age 3 years, any 3 predictors had a sensitivity of 82% and specificity of 47% for malaria. An Olaleye score ≥ 5 had a sensitivity of 62% and a specificity of 51%.

Conclusion:

In hyperendemic areas, the sensitivity of our algorithm may permit presumptive diagnosis of malaria in children. Algorithm positive cases can be presumptively treated, and negative cases can undergo parasitological testing to determine need for treatment.

The effect of nutritional rickets on bone mineral density

CONTEXT

Nutritional rickets is caused by impaired mineralization of growing bone. The effect of nutritional rickets on areal bone mineral density (aBMD) has not been established.

OBJECTIVE

Our objective was to determine if aBMD is lower in children with active rickets than in healthy control children. We expected that the reduction in aBMD would vary between the radial and ulnar metaphyses near the growth plates and the proximal diaphyses.

DESIGN

Case-control study.

SETTING

Primary care outpatient department of a teaching hospital in Jos, Nigeria.

PARTICIPANTS

Nigerian children with radiographically-confirmed rickets were compared with a reference group of control children without rickets from the same community.

MAIN OUTCOME MEASURES

Forearm bone density measurements were performed in all children with pDXA. Age, sex, and height-adjusted bone density parameters were compared between children with rickets and control subjects.

RESULTS

A total of 264 children with active rickets (ages 13-120 months) and 660 control children (ages 11-123 months) were included. In multivariate analyses controlling for height, age, and gender, rickets was associated with a 4% greater bone area and 7% lower aBMD of the radial and ulnar metaphyses compared with controls (P < .001). The effects of rickets on the diaphyses of the radius and ulna were more pronounced with an 11% greater bone area, 21% lower aBMD, and 24% lower bone mineral apparent density than controls (P < .001). In children with rickets, aBMD values were unrelated to dairy product intake or serum calcium, phosphorus, alkaline phosphatase, or 25-hydroxyvitamin D. Metaphyseal aBMD was positively associated with radiographic severity score, attributed to bone edge detection artifact by densitometry in active rickets.

CONCLUSION

Rickets results in increased bone area and reduced aBMD, which are more pronounced in the diaphyseal than in the metaphyseal regions of the radius and ulna, consistent with secondary hyperparathyroidism, generalized osteoid expansion and impaired mineralization.