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Author(s): Oxley, Anthony; Engle-Stone, Reina; Miller, Jody C; Reario, MF Dolly; Stormer, Ame; Capanzana, Mario V; Cabanilla, Carl VD; Haskell, Marjorie J; Lietz, Georg | Abstract: BackgroundThe retinol isotope dilution (RID) method has been used to evaluate vitamin A (VA) status in healthy adults and children in low- and middle-income countries (LMIC) and to assess the efficacy of various VA interventions.ObjectiveThe study was designed to examine whether dried serum spots (DSS) can be applied to RID when conducting VA total body store (TBS) assessments in community settings.MethodsFour days after an oral dose of 0.4nmg [13C10]retinyl acetate was administered to Filipino children (12-18nmo), a single blood draw was divided to isolate both serum and plasma. Serum (40 μL) was spotted and dried on Whatman 903 cards and shipped at ambient temperature whereas liquid plasma (LP) was frozen at -80°C and shipped on dry ice. The VA tracer to tracee ratio from DSS and LP was quantified by LC-MS/MS. Comparisons between DSS and LP paired samples (nn=n72) were made for [13C10]retinol specific activity (SAp) by Pearson's correlation and for VA TBS by Bland-Altman analysis.ResultsThe sum of 3 coextracted DSS were required to consistently detect [13C10]retinol above the LC-MS/MS limit of quantitation (LOQ). [13C10]retinol SAp from DSS was highly correlated with SAp from LP (rn=n0.945; P ln0.01). A comparison of methods for TBS determination using Bland-Altman analysis indicated agreement with an intraindividual difference of 24.7nμmol (4.6%). Mean total liver reserve (TLR) values from DSS and LP were 1.7nμmol/g (± 0.6 SD) and 1.6nμmol/g (± 0.6 SD), respectively.ConclusionsVA TBS can be determined from DSS thereby reducing the logistics and cost of maintaining a cold chain by shipping samples at ambient temperature and, thus, making the RID technique more feasible in LMIC community settings. This trial was registered at https://clinicaltrials.gov as NCT03030339.

OBJECTIVES: We aimed to develop and validate a tool to estimate vitamin A (VA) intake and identify children at risk of intake above the tolerable upper intake level (UL). METHODS: We developed, pilot-tested, and refined a screening tool to estimate VA intake among Filipino children 12–18 mo of age. Data were entered into tablets with pre-loaded food composition data to calculate VA intake immediately. The screening tool was used to identify children likely to have “adequate” (one group: 200–500 µg retinol activity equivalents, RAE/d) or “high” (two groups: >600 µg retinol/d) intake. Interviewers administered four 24-h recalls, one 12-h observed weighed record with 12-h recall, and a 30-d supplement questionnaire. Breastmilk intake and VA concentration were measured among breastfeeding children. We compared the screening tool and detailed dietary assessment (DDA) results for primary VA sources, group mean usual intake, and prevalence of intakes above the UL. RESULTS: Major VA sources were similar between methods: fortified milk powders, multivitamin supplements, and breastmilk; contributions from intervention programs (e.g., micronutrient powders, fortified staple foods) were low. Mean usual retinol intakes for the high groups (n = 47 and 39, respectively) were 1218 and 1313 µg/d by screening tool vs. 1096 and 931 by DDA; 70 and 77% had usual intake above 600 µg/d. In the adequate group (n = 37), mean total VA intake was 375 and 559 µg RAE/d by screening and DDA, respectively. CONCLUSIONS: This screening tool provides a reasonably good rapid estimate of VA intake among Filipino children and can be useful for identifying groups with adequate to excessive intakes. FUNDING SOURCES: Bill & Melinda Gates Foundation.

OBJECTIVES: The retinol isotope dilution method has been successfully applied to assess the efficacy of VA interventions in low and middle-income countries. However, the current method is limited in its applicability because it relies on keeping serum samples in the cold chain. To overcome that limitation, we assessed the feasibility of using DSS for assessing TBS in Filipino children 12–18 months of age. METHODS: Serum (40 µL) from Filipino children, who had received an oral dose of [,(13)C(10)]-retinyl acetate was spotted and dried on Whatman 903 cards then stored at −20°C before shipment at room temperature; aliquots of liquid serum were kept frozen at −80°C until analysis. DSS and liquid serum were extracted by established methods and then analysed by LC-MS/MS to quantify the [,(13)C]/[,(12)C] retinol ratio and TBS. RESULTS: Mean ± SD TBS of 57 Filipino infants aged 12–18 mo were 507.6 ± 185.8 µmol and 495.5 ± 170.1 µmol from either serum or DSS samples, respectively. Comparison of methods using Bland-Altman analysis indicated agreement between both methods with an intra-individual mean difference for TBS of 22.1 µmol (4.5%). CONCLUSIONS: TBS can be determined using serum spot samples in field settings, thus reducing the costs and limitations of shipping serum samples on dry ice and reducing the need for −80C storage in field stations. FUNDING SOURCES: Medical Research Council UK; Bill and Melinda Gates Foundation.