Table 1. Biomarker estimation methods and cutoffs used for specific diagnoses.
| Biomarkers (estimation method) | Cutoffs used | |
|---|---|---|
| Anaemia (WHO, 2011)7 | Blood haemoglobin* (cyanmethaemoglobin method, photometric estimation; LH750, Beckman Coulter, Brea, CA, USA) | WHO-based cutoffs: <11 g/dL for 1–4 years; <11·5 g/dL for 5–11 years; <12 g/dL for 12–14 years; <13 g/dL for 15–19 years, male individuals; <12 g/dL for 15–19 years, female individuals |
| Iron deficiency (WHO, 2020)11 | Serum ferritin (two-site immunoassay with direct chemiluminescence; Centaur, Siemens, Chicago, IL, USA) | <12 μg/L for 1–4 years, <15 μg/L for 5–19 years |
| Iron deficiency (Siemens N latex serum transferrin kit-based cutoff) | Serum transferrin receptor (particle enhanced immunonephelometry; BN II, Siemens) | ≥1·76 mg/L |
| Folate deficiency (de Benoist, 2008)12 | Erythrocyte folate (competitive immunoassay with direct chemiluminescence; Centaur) | <151 ng/mL |
| Vitamin B12 deficiency (de Benoist, 2008)12 | Serum cyanocobalamin (immunoassay with direct chemiluminescence; Advia Centaur, Siemens) | <203 pg/mL |
| Vitamin A deficiency (WHO, 2011b)5 | Serum retinol (HPLC, reverse phase chromatography) | <20 μg/dL |
| Zinc deficiency (IZincG 2004)13 | Serum zinc (flame atomic absorption spectrometry with deuterium correction) | <65 μg/dL for 1–9 years; for 10–19 years: <74 μg/dL for fasting male individuals, <70 μg/dL for fasting female and non-fasting male individuals, <66 μg/dL for non-fasting female individuals |
| High risk for renal dysfunction (Williamson, 2011)14 | Serum creatinine (spectrophotometry, alkaline picrate—kinetic IFCC IDMS standardised) | >0·7 mg/dL for 5–12 years, >1·0 mg/dL for 13–19 years |
| Hypercholesterolaemia (Expert Panel, 2011)15 | Serum total cholesterol (spectrophotometry, cholesterol oxidase esterase peroxidase) | ≥200 mg/dL for 5–19 years |
| Impaired glucose homoeostasis including diabetes (Expert Panel, 2011)15 | Glycosylated haemoglobin (HPLC) | >5·6% for 5–19 years |
| Hypoalbuminaemia (Kim et al, 2017)16 | Serum albumin (spectrophotometry, BCP dye binding) | <3·5 g/dL for 5–19 year |
| Inflammation (Namaste et al, 2017)17 | Serum CRP (particle-enhanced Immunonephelometry; BN II) | >5 mg/L |
| Haemoglobinopathy (Bain and Lewis, 2012)18 | Variant haemoglobins (HPLC; CDM system, Bio-Rad, Hercules, CA, USA) | Haemoglobin A2 3·5–9·0% for the thalassaemia trait, any haemoglobin S for sickle cell |
BCP=bromocresol purple. CRP=C-reactive protein. HPLC=high-performance liquid chromatography. IDMS=isotope dilution mass spectrometry. IFCC=International Federation of Clinical Chemistry and Laboratory Medicine.
*
Haemoglobin concentrations were adjusted for altitude in survey enumeration areas higher than 1000 m.