Table 1 Guideline definition of ID in general population and chronic disease; summary of current ID laboratory measurements

General population

 WHO [38]

International

2020

ID in

–

sTfR#, CRP**

˗ Infants and children < 5 years

 < 12

  with infection/inflammation

 < 30

˗ Children > 5 years, adolescents, adults, older person (60 + years)

 < 15

  with infection/inflammation

 < 70

˗ Pregnant women (only for first trimester)

 < 15

 AAFP [39]

American

2013

IDA

 < 30

–

low serum iron^#, low TSAT^#, high TIBC^#

with infection/ inflammation

 < 50

 BCG [40]

British

2019

ID in children

 < 12

additional < 20

serum iron^#, TIBC^#, TSAT

- Possible ID

12–20

ID in adults

 < 15

- Probable ID

15–30

- Unlikely ID

 > 30

  or with chronic inflammatory disease

 > 70–100

  or in elderly patients

 > 50

Chronic heart failure (HF)

 ACCF/AHA [30]

American

2017

AID

 < 100

–

–

FID

or 100–300

and < 20

 ESC [23]

European

2021

AID

 < 100

and < 20

sTfR^#

FID

or 100–299

and < 20

Chronic kidney disease (CKD)

 KIDIGO [31]

International

2012

IDA only

–

–

–

ND/HD-CKD + IDA

 ≤ 500

and ≤ 30

Pediatric CKD + IDA

 ≤ 100

and ≤ 20

Severe ID

 ≤ 30

–

 KDOQI [32]

American

2013

IDA only

–

–

–

 ERBP [33]

European

2013

ID/IDA (AID)

 < 100

and < 20

–

 UK NICE [34]

British

2021

IDA only

 < 100*

and < 20*

Red blood cell markers:

%HRC > 6%, CHr < 29 pg

 JSDT [35]

(2015 version)

Japanese

2017

HD-CKD + ID

 ≤ 100

 ≤ 20

–

Inflammatory bowel disease (IBD)

 ECCO [21]

European

2015

ID/IDA (quiescent disease, without inflammation)

 < 30

–

Tests to distinguish between IDA and ACD: sTfR,

sTfR–ferritin index

AID and ACD

30–100

and/or < 20

FID and ACD

 > 100

and < 20

 BSG [36]

British

2021

ID/IDA (AID)

 < 15

–

sTfR^# (in healthy subjects), sTfR–ferritin index^#, CHr^#, HYPO%^# (in chronic disease and/or raised ESR^#, CRP)

FID

 ≥ 100

 < 20

Cancer

 NCCN [37]

America

2021

ID/IDA (AID)

 < 30

and < 20

–

FID (often when receiving ESAs)

30–500

and < 50

Possible FID

 > 500–800

and < 50

 ESMO [20]

European

2018

ID/IDA (AID)

 < 30–100

and < 20

AID: sTfR^#, ZPP^#

AID and FID: %HYPO > 5%,

CHr < 28 pg, CRP**

FID

 > 100

and < 20

 DGHO [11]

Germany

2022

ID/IDA (AID)

 < 30–100

 < 20

sTfR > 0.76–1.76 mg/L (Dade Behring Test), sTfR–ferritin index > 0.2–3.7 men, > 0.6–3.8 women (Roche Test), ZPP > 80 µmol/mol Häm, HYPO% > 10%, CHr < 26 pg, CRP**

FID

100–800

and < 20