The laboratory analyses were carried out by the Research Laboratory of Preventive Medicine of the Republic of Tajikistan in Dushanbe in early 2017. Serum samples were analysed using enzyme‐linked immunosorbent assays to assess SF (BioVendor GmbH, cat nr: RCD012R), TfR (BioVendor GmbH, cat nr: RD194011100), C‐reactive protein (CRP, BioVendor GmbH, cat nr: RAP001), RBP (Abcam, cat nr: ab196264), vitamin D (Enzo Life Sciences, Inc., cat nr: ADI‐900‐215), and serum folate (antibodies‐online Inc., cat nr: ABIN857086). Analyses were conducted according to the manufacturer recommendations (including high and low controls on each plate). In addition, an internal control, a pooled serum sample, was included with each batch and used for interplate variation analysis and quality control assessments.
UIC in spot urine was measured using the Pino modification of the Sandell–Kolthoff reaction with spectrophotometric detection (Caldwell, Makhmudov, Jones, & Hollowell,2005 ; Pino, Fang, & Braverman, 1996 ). All analyses were done using nanopure grade water, and all laboratory glassware and plasticware were acid washed before use. Internal controls were used for the UIC analysis.
UIC in spot urine was measured using the Pino modification of the Sandell–Kolthoff reaction with spectrophotometric detection (Caldwell, Makhmudov, Jones, & Hollowell,