Challenges and Lessons Learned in Generating and Interpreting NHANES Nutritional Biomarker Data

Inflammatory biomarkers mediate the association between polycyclic aromatic hydrocarbon exposure and dyslipidemia: a national population-based study

Exploring the association between exposure to polycyclic aromatic hydrocarbons (PAHs) and the risk of dyslipidemia and possible mediating effects is essential for conducting epidemiological health studies on related lipid disorders. Therefore, our study aimed to elucidate the potential association between PAH exposure and dyslipidemia risk and further identify the mediating effects based on blood cell-based inflammatory biomarkers. This cross-sectional study was conducted on 8,380 individuals with complete survey data from the National Health and Nutrition Examination Survey (2001-2016). Multiple models (generalized linear regression model, restricted cubic spline model, Bayesian kernel machine regression, weighted quantiles sum regression) were used to assess the relationship between PAH co-exposure and the dyslipidemia risk and further identify potential mediating effects. Among the 8380 subjects, 2886 (34.44 %) had dyslipidemia. After adjusting for the confounding factors, the adjusted OR and 95% CI for dyslipidemia in the highest quartile of subjects were 1.30 (1.11, 1.51), 1. 22 (1.04, 1.43), 1.21 (1.03, 1.42), 1.29 (1.10, 1.52), 1.18 (1.01, 1.37), and 1.04 (0.89, 1.23) for 1-hydroxynaphthalene, 2-hydroxynaphthalene, 3-hydroxyfluorene, 2-hydroxyfluorene (2-FLU), 1-hydroxyphenanthrene, and 1-hydroxypyrene. The Bayesian kernel machine regression model also showed a positive correlation between PAH mixtures and dyslipidemia, and 2-FLU has the highest contribution. Mediation effect analyses showed that white blood cells and neutrophils were statistically significant in the association between PAHs and dyslipidemia. The present study suggests that individual and mixed PAH exposures may increase the risk of dyslipidemia in adults. Inflammatory biomarkers significantly mediated the relationship between PAH exposure and dyslipidemia. Environmental pollutants and their mechanisms should be more intensively monitored and studied.

Lower Intakes of Key Nutrients Are Associated with More School and Workplace Absenteeism in US Children and Adults: A Cross-Sectional Study of NHANES 2003-2008

The influence of individual macro- and micronutrients on absenteeism in the United States is largely unknown. The objective of this study was to determine whether nutritional status or nutrient intake were associated with absenteeism from school and work due to illness or injury. Data from NHANES 2003-2008 were used to assess nutrient intake from food and food plus supplements, nutritional biomarker levels, and school and work absenteeism per year in children and adults. Negative binomial regression models were used to predict mean days of missed work per year and to estimate incidence rate ratios (IRRs) of absenteeism by nutrient biomarker status. Of 7429 children, 77% reported missing school days (mean 4.0 days). Of 8252 adults, 51% reported missing work days (mean 4.9 days). Children and adults who reported more absent days had a significantly lower intake of protein and several essential micronutrients from the diet. When nutrients from supplements were included, this negative association was retained for protein, selenium, choline, and DHA in children and for protein, selenium, vitamin K, choline, potassium, fiber, octadecatrienoic acid, and lycopene in adults. Future studies are needed to ascertain whether dietary interventions, such as access to healthier food options and/or dietary supplements, can reduce absenteeism.

Integrated multiomic wastewater-based epidemiology can elucidate population-level dietary behaviour and inform public health nutrition assessments

Population-level nutritional assessments often rely on self-reported data, which increases the risk of recall bias. Here, we demonstrate that wastewater-based epidemiology can be used for near real-time population dietary assessments. Neighbourhood-level, untreated wastewater samples were collected monthly from within an urban population in the south-western United States from August 2017 to July 2019. Using liquid chromatography-tandem mass spectrometry, we identify recurring seasonal dynamics in phytoestrogen consumption, including dietary changes linked to the winter holiday season. Using 16S ribosomal RNA gene amplicon sequencing, we demonstrated the feasibility of detecting sewage-derived human gut bacterial taxa involved in phytoestrogen metabolism, including Bifidobacterium, Blautia and Romboutsia. Combined metabolomic and genomic wastewater analysis can inform nutritional assessments at population scale, indicating wastewater-based epidemiology as a promising tool for actionable and cost-effective data collection to support public health nutrition.

Systematic scoping review evaluating the potential of wastewater-based epidemiology for monitoring cardiovascular disease and cancer

Cardiovascular disease (CVD) and cancer are collectively responsible for tens of millions of global deaths each year. These rates are projected to intensify as the COVID-19 pandemic has caused delays in individualized diagnostics, or exacerbated prevalence due to Post Acute Coronavirus (COVID-19) Syndrome. Wastewater-based epidemiology (WBE) has successfully been employed as a useful tool for generating population-level health assessments, and was examined here in this systematic scoping literature review to (i) identify endogenous human biomarkers reported to indicate CVD or cancer in clinical practice, (ii) assess specificity to the indicated diseases, (iii) evaluate the utility for estimating population-level disease prevalence in community wastewater, and (iv) contextualize the obtained information for monitoring CVD and cancer presence via WBE. A total of 48 peer-reviewed papers were critically examined identifying five urinary protein biomarkers: cardiac troponin I (cTnI) (heart attack/heart failure), cystatin C (atherosclerosis), normetanephrine (tumor presence), α-fetoprotein (prostate and liver cancer), and microtubule assisted serine/threonine kinase 4 (MAST4) (breast cancer). Next, urinary excretion information was utilized to predict biomarker concentrations extant in community wastewater, resulting in average healthy concentrations ranging from 0.02 to 1159 ng/L, and disease-indicating thresholds from 0.16 to 3041 ng/L. Finally, estimating prevalence-adjusted wastewater measurements was explored in order to assess community-level CVD and cancer presence utilizing U.S. reported prevalence rates. Results obtained suggest that WBE can serve as a viable tool in support of current methods for CVD and cancer assessment to reduce morbidities and mortalities worldwide.

Magnesium Depletion Score is Associated with Long-Term Mortality in Chronic Kidney Diseases: A Prospective Population-Based Cohort Study

BACKGROUND

Magnesium deficiency is common in patients with chronic kidney diseases (CKD) due to restricted magnesium intake and impaired magnesium reabsorption. Based on pathophysiological risk factors influencing kidney magnesium reabsorption, a magnesium depletion score (MDS) was developed. Using MDS as a novel indicator for assessing body magnesium status, we hypothesized that it was associated with clinical prognosis.

METHODS

We conducted a prospective population-based cohort study using data from the National Health and Nutrition Examination Survey 1999-2014 to explore the impact of MDS on the clinical outcomes of CKD patients. Propensity score-matched analyses were conducted to increase comparability. The primary outcome was all-cause mortality, and the secondary outcomes were cardiovascular-cause and cancer-cause mortality.

RESULTS

After propensity score matching, 3294 CKD patients were divided into 2 groups: MDS ≤ 2 (N = 1647), and MDS > 2 (N = 1647). During a median follow-up of 75 months, Kaplan-Meier analyses showed that MDS > 2 was associated with worse 5- and 10-year overall survival (78.5% vs 73.4%; 53.1% vs 43.1%, P < 0.001). After adjusting for confounding variables, MDS was found to be an independent risk factor for all-cause mortality (HR:1.34, 95% CI 1.20-1.50, P < 0.001). MDS > 2 was also associated with higher cardiovascular-cause mortality (16.2% VS 11.6%, P = 0.005). Multivariate competing risk analysis revealed that MDS > 2 was an independent risk factor (HR: 1.33, 95% CI 1.06-1.66, P = 0.012). Subgroup analyses reported that MDS > 2 increased all-cause mortality and cardiovascular-cause mortality only in patients with inadequate magnesium intake (P < 0.001, P < 0.001) but not in those with adequate intake (P = 0.068, P = 0.920).

CONCLUSIONS

A magnesium depletion score > 2 was independently associated with higher long-term cardiovascular-cause and all-cause mortality in CKD patients.

Longitudinal trends in produce purchasing behavior: a descriptive study of transaction level data from loyalty card households

Background

Household food purchases (HFP) are in the pathway between the community food environment and the foods available in households for consumption. As such, HFP data have emerged as alternatives to monitor population dietary trends over-time. In this paper, we investigate the use of loyalty card datasets as unexplored sources of continuously collected HFP data to describe temporal trends in household produce purchases.

Methods

We partnered with a grocery store chain to obtain a loyalty card database with grocery transactions by household from January 2016-October 2018. We included households in an urban county with complete observations for head of household age group, household income group, and family size. Data were summarized as weighted averages (95% CI) of percent produce purchased out of all foods purchased by household per month. We modeled seasonal and linear trends in the proportion of produce purchases by age group and income while accounting for repeated observations per household using generalized estimating equations.

Results

There are 290,098 households in the database (88% of all county households). At baseline, the smallest and largest percent produce purchases are observed among the youngest and lowest income (12.2%, CI 11.1; 13.3) and the oldest and highest income households (19.3, CI 18.9; 19.6); respectively. The seasonal variations are consistent in all age and income groups with an April-June peak gradually descending until December. However, the average linear change in percent produce purchased per household per year varies by age and income being the steepest among the youngest households at each income level (from 1.42%, CI 0.98;1.8 to 0.69%, CI 0.42;0.95) while the oldest households experience almost no annual change.

Conclusions

 We explored the potential of a collaboration with a food retailer to use continuously collected loyalty card data for public health nutrition purposes. Our findings suggest a trend towards a healthier pattern in long-term food purchases and household food availability among the youngest households that may lessen the population chronic disease burden if sustained. Understanding the foods available for consumption within households allows public health advocates to develop and evaluate policies and programs promoting foods and nutrients along the life course.

The Relationship Between Ferritin and BMI is Mediated by Inflammation Among Women in Higher-Income Countries, But Not in Most Lower-Income Countries Nor Among Young Children: A Multi-Country Analysis

Background

In the presence of inflammation, the serum or plasma ferritin concentration ("ferritin" hereafter) transiently increases, confounding its interpretation as an iron status marker. The extent to which adiposity-related inflammation may influence ferritin interpretation is uncertain.

Objectives

We describe relationships between weight status, inflammation, and ferritin among nonpregnant women of reproductive age (WRA; 15-49 years) and preschool-age children (PSC; 6-59 months) with normal weight to overweight or obesity (OWOB) in differing geographic settings.

Methods

Cross-sectional data were separately analyzed from 18 surveys (WRA) and 25 surveys (PSC) from the Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project, excluding observations with underweight, wasting, pregnancy, or malaria. Relationships were assessed between BMI (in WRA) or BMI-for-age z-score (BAZ; in PSC), inflammatory biomarkers of C-reactive protein (CRP) and/or α-1-acid glycoprotein (AGP), ferritin by linear regression, and potential mediation by CRP and/or AGP in relationships between BMI or BAZ and ferritin with structural equation modeling. Regression and mediation models accounted for complex survey designs. Results were grouped by World Bank income classifications.

Results

In 5 of 6 surveys among WRA from upper-middle and high-income countries, ferritin was significantly positively associated with BMI, and this relationship was partially (or fully, in the United States) mediated by CRP and/or AGP. Mediation was present in 4 of 12 surveys for WRA in low- and lower-middle income countries. Among PSC, ferritin was positively associated with CRP and/or AGP in all surveys, but there were no significant CRP- or AGP-mediated relationships between ferritin and BAZ, except a negative relationship in the Philippines.

Conclusions

Where having OWOB is common among WRA, measurements of inflammatory biomarkers and their uses in interpreting ferritin may improve iron status assessments. While these relationships were inconsistent among PSC, inflammation was common and should be measured to interpret iron status. Included Kenyan trial data are registered at clinicaltrials.gov as NCT01088958.

Associations of Urine Specific Gravity With Body Mass Index and Lean Body Mass at the Population Level: Implications for Hydration Monitoring

Urine specific gravity (USG) thresholds are used in practice and research to determine hypohydration. However, some limited research has found that body size and body composition may impact USG, suggesting that fixed cutoffs may be insensitive. Cross-sectional data from 3,634 participants of the 2007-2008 National Health and Nutrition Examination Survey were analyzed. Along with USG, body mass index (BMI), estimated lean body mass (LBM), and dietary intake were quantified. Logistic regression models were used to evaluate whether higher quintiles of BMI and LBM were associated with elevated USG (USG ≥ 1.020 and ≥1.025) after accounting for dietary moisture and sodium. The USG (1.018 ± 0.0003 vs. 1.015 ± 0.0004); BMI (28.4 ± 0.2 vs. 28.0 ± 0.2 kg/m2); LBM (60.9 ± 0.3 vs. 42.2 ± 0.2 kg); dietary moisture (3,401 ± 92 vs. 2,759 ± 49 g/day); and dietary sodium (4,171 ± 85 vs. 2,959 ± 50) were greater in men than in women (p < .05). Men and women in the fifth quintiles of BMI or LBM (vs. Quintile 1) had greater odds (2.00-3.68, p < .05) of elevated USG. (The only exception was for the association between BMI and USG ≥ 1.025 in men.) Being in Quintile 4 of LBM or BMI (vs. Quintile 1) also tended to be associated with higher odds of elevated of USG, though this pattern was more consistent when using USG ≥ 1.020 than USG ≥ 1.025. In summary, BMI and LBM are associated with USG at the population level. These results affirm that USG depends on body size and composition and raise questions about using fixed USG thresholds for determining hypohydration, particularly for people in the upper quintiles of BMI and LBM.

Associations between elevated kidney and liver biomarker ratios, metabolic syndrome and all-cause and coronary heart disease (CHD) mortality: analysis of the U.S. National Health and Nutrition Examination Survey (NHANES)

BACKGROUND

We examined the relationship between ratios of select biomarkers of kidney and liver function on all-cause and coronary heart disease (CHD) mortality, both in isolation, and in combination with metabolic syndrome (MetS), among adults (20 + years, n = 10,604).

METHODS

Data was derived from the U.S. National Health and Nutrition Examination Survey (1999-2016) including public-use linked mortality follow-up files through December 31, 2015.

RESULTS

Select biomarker ratios of kidney (UACR or albuminuria and BUN-CR) and liver (AST-ALT and GGT-ALP) function in isolation and in combination with MetS were associated with all-cause and CHD mortality. Compared to individuals with neither elevated biomarker ratios nor MetS (HR = 1.00, referent), increased risk of all-cause mortality was observed in the following groups: MetS with elevated UACR (HR, 95% CI = 2.57, 1.99-3.33), MetS with elevated AST-ALT (HR = 2.22, 1.61-3.07), elevated UACR without MetS (HR = 2.12, 1.65-2.72), and elevated AST-ALT without MetS (HR = 1.71, 1.35-2.18); no other biomarker ratios were associated with all-cause mortality. For cause-specific deaths, elevated risk of CHD mortality was associated with MetS with elevated UACR (HR = 1.67, 1.05-2.67), MetS with elevated AST-ALT (HR = 2.80, 1.62-4.86), and elevated BUN-CR without MetS (HR = 2.12, 1.12-4.04); no other biomarker ratios were associated with CHD mortality.

CONCLUSION

Future longitudinal studies are necessary to examine the utility of these biomarker ratios in risk stratification for chronic disease management.

Clinically-diagnosed vitamin deficiencies and disorders in the entire United States military population, 1997-2015

Background

This study examined incidence rates, temporal trends, and demographic factors associated with vitamin deficiencies/disorders in all United States military personnel from 1997 to 2015 (mean N = 1,382,266/year).

Methods

Employing an ecological study design, the Defense Medical Epidemiological Database and specific International Classification of Diseases codes were used to determine incidence rates for clinically-diagnosed vitamin deficiencies/disorders. Associations with demographic factors were examined.

Results

The overall incidence rate of vitamin deficiencies/disorders was 92.7 cases/100,000 person-years (p-yr). Highest rates were for vitamin D (53.7 cases/100,000 p-yr), other B-complex vitamins (20.2 cases, 100,000 p-yr), vitamin B₁₂ anemia (7.6 cases/100,000 p-yr), deficiencies of “other vitamins” (5.9 cases/100,000 p-yr), and vitamin A (2.5 cases/100,000 p-yr). Thiamin, riboflavin, niacin, pyridoxine, folate, vitamin C, and vitamin K deficiencies and hypervitaminoses A and D had < 1 case/100,000 p-yr. Rates for vitamin D, other B-complex, “other vitamin”, and thiamin deficiencies increased over time, while vitamin A and C deficiencies decreased. Women had higher incidence rates for all examined deficiencies/ disorders except niacin and vitamin C. Incidence rates rose with age in 8 of 15 deficiency/disorder categories and blacks had higher incidence rates in 9 of 15 deficiency/disorder categories.

Conclusions

The overall rate of clinically-diagnosed vitamin deficiencies and disorders was low but higher in women and minority subgroups. As for most illnesses, the diagnosed incidence of such disorders may be an underestimate of the actual incidence. These findings can guide clinical decision making with regard to testing for nutritional deficiencies and delivering public health information to at risk populations.

Clinical trial registration

(No. ISRCTN58987177). Registration date 9 October 2019.

Discrepancies between actual weight, weight perception and weight loss intention amongst persons with NAFLD

BACKGROUND

Currently, weight loss remains the main management strategy for NAFLD, but the weight loss intention and methods remain poorly characterized.

METHODS

We analysed data about the perception of weight status, intention and methods to lose weight amongst 3,822 persons with NAFLD (United States Fatty Liver Index ≥ 30) from the National Health and Nutrition Examination Survey, 2001-2014.

RESULTS

Only 53.9% of people with NAFLD intended to lose weight, 91.8% with perception of overweight and 8.2% with normal weight perception. Persons with perception of overweight or overweight/obese status were four times more likely to try to lose weight (adjusted odds ratios 3.9 and 4.2, respectively, both P < 0.0001). Younger age, women, higher educational level, Hispanic and blacks (versus whites) were significant independent factors associated with weight loss intention. Notably, ≤10% attended weight loss programme. Metabolic equivalent of task hours per week was significantly higher in whites who exercised to lose weight (vs. no exercise, P = 0.003) but not in other racial/ethnic groups. Interestingly, calorie intake was similar between those who dieted versus not (2056 vs. 1970 kcal/day, P = 0.11). About 30% reported ≥ 10-lb weight loss, with 50% higher odds of success for men but there was no difference by race/ethnicity.

CONCLUSION

Overweight or obese perception was a key driver in weight loss activities but was inconsistent with actual weight status and varied by race/ethnicity and other sociodemographic factors. Weight loss programme is under-utilized and should take in account of weight perception training and culturally appropriate approach.

Clinical Relevance of Urine Flow Rate and Exposure to Polycyclic Aromatic Hydrocarbons

Background: Polycyclic aromatic hydrocarbon (PAH) metabolites have received increasing attention because several of these organic substances are highly carcinogenic or mutagenic. Exposure to PAHs is associated with many harmful health effects; however, we are not aware of any study that has explored the exposure to PAHs and urinary conditions in the general population. The present work aimed to investigate the correlation among PAH and urine flow rate (UFR). Method: Cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 2009–2012 were used in our study. A total of 4172 participants and a total of nine PAH metabolites were examined. The UFR was measured as the amount of urine excreted in a period of time (mL/h). Several covariates were adjusted in linear regression models. Result: After adjusting for variables, the PAH metabolites in urine showed a significant correlation with UFR. Dose-dependent associations between PAH metabolites in the urine and UFR were also found. Higher quartiles of PAH metabolites in urine exhibited higher regression coefficients. Conclusion: Our study highlighted that PAH metabolites in urine had a strong association with decreased UFR in the US adult population. These findings support the possibility that PAH exposure is related to bladder dysfunction. Further prospective studies are warranted.

Interpretation of vitamin B-12 and folate concentrations in population-based surveys does not require adjustment for inflammation: Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project

BACKGROUND

Vitamin B-12 and folate deficiencies in women and children have important public health implications. However, the evidence is conflicting and limited on whether the influence of inflammation on biomarker concentrations may be sufficiently and consistently influenced by inflammation to require adjustment for interpreting concentrations or estimating population prevalence of deficiencies.

OBJECTIVE

We examined correlations between concentrations of the inflammation biomarkers C-reactive protein (CRP) and α1-acid glycoprotein (AGP) and serum vitamin B-12 and serum and RBC folate among nonpregnant women of reproductive age (WRA; 15-49 yr) and preschool children (PSC; 6-59 mo).

METHODS

We analyzed cross-sectional data from 16 nationally representative nutrition surveys conducted in WRA (n = 32,588) and PSC (n = 8,256) from the Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia project. Spearman correlations between CRP or AGP and vitamin B-12 or folate concentrations were examined, taking into account complex survey design effects.

RESULTS

Correlations between inflammation and vitamin B-12 or folate were weak, with no clear pattern of association in either WRA or PSC. Correlation coefficients between CRP and vitamin B-12 for WRA and PSC ranged from -0.25 to 0.16, and correlations between AGP and vitamin B-12 ranged between -0.07 and 0.14. Similarly, correlations between CRP and serum folate ranged from -0.13 to 0.08, and correlations between AGP and serum folate between -0.21 and 0.02. Only 3 surveys measured RBC folate, and among them, correlations for WRA ranged from -0.07 to 0.08 for CRP and -0.04 for AGP (1 country).

CONCLUSIONS

Based on the weak and inconsistent correlations between CRP or AGP and vitamin B-12 or folate biomarkers, there is no rationale to adjust for inflammation when estimating population prevalence of vitamin B-12 or folate deficiencies in WRA or PSC.

Data-driven physiologic thresholds for iron deficiency associated with hematologic decline

Iron-deficiency contributes to a ∼50% of anemia prevalence worldwide, but reference intervals for iron status tests are not optimized for anemia diagnosis. To address this limitation, we identified the serum ferritin (SF) thresholds associated with hematologic decline in iron-deficient patients, and the SF thresholds from which an SF increase was associated with hematologic improvement. Paired red blood cell and SF measurements were analysed from two adult cohorts at Massachusetts General Hospital (MGH), from 2008-2011 (N = 48 409), and 2016-2018 (N = 10 042). Inter-patient measurements in the first cohort were used to define optimal SF thresholds based on the physiologic relationship between SF and red cell measurements. Intra-patient measurements (1-26 weeks apart) in the second cohort were used to identify SF thresholds from which an SF increase was associated, with an increase in red cell measurements. The identified optimal SF thresholds varied with age, sex and red cell measure. Thresholds associated with a ∼5% decline in red cell index were typically in the range 10-25 ng/mL. Thresholds for younger women (18-45 year) were ∼5 ng/mL lower than for older women (60-95 years), and ∼10 ng/mL lower than for men. Thresholds from which a subsequent increase in SF was associated with a concomitant increase in red cell measure showed similar patterns: younger women had lower thresholds (∼15 ng/mL) than older women (∼25 ng/mL), or men (∼35 ng/mL). These results suggest that diagnostic accuracy may be improved by setting different SF thresholds for younger women, older women, and men. This study illustrates how clinical databases may provide physiologic evidence for improved diagnostic thresholds.

Point-of-Care Assessment of Folate Status in Women of Reproductive Age Using a Fluorescence Lateral Flow Assay

Folate is an essential vitamin to the development of a fetus in early pregnancy. Maternal folate supplementation around the time of conception has been shown to decrease the risk of neural tube defects (NTDs), a class of serious birth defects. The closure of the neural tube before the 28th day after conception necessitates that the folate intake must take place before most women know that they are pregnant. Therefore, screening women of reproductive age for folate status would allow for an improved understanding of the need for supplementation in women who could become pregnant as well as the effectiveness of current supplementation and fortification recommendations. Current folate assessment is limited to labbased assays which require expensive equipment, trained personnel, and are time-intensive. Our point-of-care diagnostic test quantifies levels of folate in human serum with the use of a lateral flow assay and a portable imaging device. We have designed an assay which uses fluorescent particles, folate binding protein, and antibodies to measure serum folate. This test could be used in resource-limited settings, where access to laboratory infrastructure is limited and where knowledge of folate status in women of reproductive age is lacking. By increasing our understanding of folate status around the world, we can improve implementation of folic acid supplementation and fortification and therefore reduce the risk of NTDs.

Harmonizing the Calibrator and Microorganism Used in the Folate Microbiological Assay Increases the Comparability of Serum and Whole-Blood Folate Results in a CDC Round-Robin Study

Background

Harmonizing critical reagents for the folate microbiological assay (MBA) may improve among-laboratory comparability.

Objective

We assessed the comparability of the MBA for serum folate (S-FOL) and whole-blood folate (WB-FOL) in an international comparison study.

Methods

Eight laboratories obtained a kit containing CDC microorganism inoculum (chloramphenicol-resistant Lactobacillus rhamnosus), CDC calibrator (5-methyltetrahydrofolate), and 23 serum and WB hemolysate samples each. Laboratories analyzed the samples in single measurement over 2 d using 4 conditions: in-house microorganism and in-house calibrator (IH-MO & IH-CAL), in-house microorganism and CDC calibrator (IH-MO & CDC-CAL), CDC microorganism and in-house calibrator (CDC-MO & IH-CAL), and CDC microorganism and CDC calibrator (CDC-MO & CDC-CAL). We calculated geometric mean concentrations for each laboratory and condition and compared data to the CDC MBA (target).

Results

The among-laboratory arithmetic mean S-FOL concentrations for the 4 conditions were 30.2, 28.1, 30.0, and 29.9 (group 1, 5-methyltetrahydrofolate IH-CAL) compared with 35.3, 33.3, 33.6, and 30.7 nmol/L (group 2, folic acid IH-CAL), respectively; and 428, 405, 398, and 393 (group 1) compared with 469, 423, 477, and 418 nmol/L (group 2), respectively, for WB-FOL. Differences to the CDC MBA target values were smaller for group 1 (range across conditions; S-FOL: 9.9-21%; WB-FOL: 9.0-18%) compared with group 2 laboratories (S-FOL: 13-30%; WB-FOL: 16-32%) and smaller when CDC reagents were used compared with in-house reagents (S-FOL: 12% compared with 22%; WB-FOL: 13% compared with 25%). A linear mixed model estimated a small microorganism effect (S-FOL: 2.3%; WB-FOL: 2.3%) and a larger mean calibrator effect; folic acid compared with 5-methyltetrahydrofolate calibrator produced 12% higher S-FOL and 15% higher WB-FOL results. When laboratories used CDC reagents, the estimated among-laboratory variability was ∼10% for S-FOL and WB-FOL.

Conclusion

Harmonizing the calibrator and microorganism for the folate MBA has the potential to improve the among-laboratory comparability in future surveys.

Framework for laboratory harmonization of folate measurements in low- and middle-income countries and regions

The measurement of serum and red blood cell folate, two commonly used biomarkers of folate status in populations, is complicated by analytical and data interpretation challenges. Folate results show poor comparability across laboratories, even using the same analytical technique. The folate microbiologic assay produces accurate results and requires simple instrumentation. Thus, it could be set up and maintained in low- and middle-income country laboratories. However, the assay has to be harmonized through the use of common critical reagents (e.g., microorganism and folate calibrator) in order to produce comparable results across laboratories and over time, so that the same cutoff values can be applied across surveys. There is a limited need for blood folate measurements in a country owing to the periodic nature of surveys. Having a network of regional resource laboratories proficient in conducting the folate microbiologic assay and willing and able to perform service work for other countries will be the most efficient way to create an infrastructure wherein qualified laboratories produce reliable blood folate data. Continuous participation of these laboratories in a certification program can verify and document their proficiency. If the resource laboratories conduct the work on a fee-for-service basis, they could become self-sustaining in the long run.

Dietary Supplements: Regulatory Challenges and Research Resources

Many of the scientific and regulatory challenges that exist in research on the safety, quality and efficacy of dietary supplements are common to all countries as the marketplace for them becomes increasingly global. This article summarizes some of the challenges in supplement science and provides a case study of research at the Office of Dietary Supplements at the National Institutes of Health, USA, along with some resources it has developed that are available to all scientists. It includes examples of some of the regulatory challenges faced and some resources for those who wish to learn more about them.