Table 1.

Laboratory tests

	Sample	Method	Laboratory
Complete blood count, including hemoglobin	Whole blood—collected in an EDTA tube	Automated analyzer (Sysmex XN 9000 automated hematology analyzer)	Department of Transfusion Medicine and Immunohematology, Christian Medical College, Vellore Routine test offered by this diagnostic laboratory
Serum iron and unsaturated iron-binding capacity (UIBC)	Serum sample from blood collected in clot activator tube	Automated chemistry analyzer (Roche Diagnostics GmbH), using a colorimetric method	Department of Clinical Biochemistry, Christian Medical College, Vellore Routine test offered by this diagnostic laboratory
Total iron-binding capacity (TIBC)		Calculated from values for serum iron and UIBC
Transferrin saturation		Calculated from values for serum iron and TIBC
Serum ferritin	Serum sample from blood collected in clot activator tube	Atellica IM 1600 automated immunoassay analyzer (Siemens Healthcare Diagnostics Inc.), using a chemiluminescence assay	Department of Clinical Biochemistry, Christian Medical College, Vellore Routine test offered by this diagnostic laboratory
Soluble transferrin receptor (sTfR)	Serum sample from blood collected in clot activator tube	Atellica IM 1600 automated immunoassay analyzer (Siemens Healthcare Diagnostics Inc), using a chemiluminescence assay	Department of Clinical Biochemistry, Christian Medical College, Vellore Routine test offered by this diagnostic laboratory
Non-transferrin-bound iron (NTBI)	Serum sample from blood collected in clot activator tube	NTBI will be estimated using a modified version of a published method [62] The NTBI fraction will be separated using 30-kDa filters, after reaction with a weak iron chelator (nitrilotriacetic acid). The separated NTBI will be estimated using inductively coupled plasma mass spectrometry	Departments of Biochemistry and Clinical Biochemistry, Christian Medical College, Vellore. The assay is standardized for accuracy and precision
hsCRP	Serum sample from blood collected in clot activator tube	Automated analyzer (BN Prospec Siemens analyzer (Siemens, GmbH, Marburg, Germany))	Department of Microbiology, Christian Medical College, Vellore Routine test offered by this diagnostic laboratory
Glucose	Plasma samples from blood collected in tubes containing sodium fluoride, at baseline (fasting) and 30, 60, 90, and 120 min after ingestion of 75 g of glucose	Automated analyzer (Roche Cobas c702 autoanalyzer), using a colorimetric method	Department of Clinical Biochemistry, Christian Medical College, Vellore Routine test offered by this diagnostic laboratory
C-peptide and insulin	Serum from blood samples collected in clot activator tubes, at baseline (fasting) and 30, 60, 90, and 120 min of the OGTT	Immulite 2000XPi automated immunoassay analyzer (Siemens Healthcare Diagnostics Inc), using a chemiluminescence assay	Department of Clinical Biochemistry, Christian Medical College, Vellore Routine test offered by this diagnostic laboratory