Definition library

In our words: Oxygenation bands (PaO2/FiO2, mm Hg): above 200 up to 300 mild; above 100 up to 200 moderate; 100 or less severe. The bands alone never establish the full syndrome.

ARDS Definition Task Force (European Society of Intensive Care Medicine initiative, endorsed by ATS and SCCM) (2012) · Abstract (Europe PMC record of PMID:22797452) · source

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In our words: Office blood pressure (adults, mm Hg): 140/90 or higher is hypertension; systolic 120 to 139 or diastolic 70 to 89 is elevated; below 120/70 is not elevated.

European Society of Cardiology (2024) · Section 5.1, Table 5 (office BP) · source

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In our words: Serum sodium below 135 mmol/L is low.

European Society of Intensive Care Medicine, European Society of Endocrinology and European Renal Association – European Dialysis and Transplant Association (ERBP) (2014) · Abstract · source

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In our words: On invasive ventilation with PEEP of at least 5 cm H2O (PaO2:FiO2, mm Hg): above 200 up to 300 mild; above 100 up to 200 moderate; 100 or less severe.

American Thoracic Society-led global consensus (Am J Respir Crit Care Med 2024;209(1):37-47) (2024) · Table 1 'Diagnostic Criteria for the New Global Definition of ARDS', intubated ARDS and footnote ¶ · source

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In our words: When FEV1/FVC after a bronchodilator is below 0.7: FEV1 80% of predicted or more is grade 1; 50 to under 80% grade 2; 30 to under 50% grade 3; under 30% grade 4. A ratio of 0.7 or more shows no obstruction by this fixed ratio.

Global Initiative for Chronic Obstructive Lung Disease (GOLD) (2026) · Figure 2.10 (PDF page 20); key points (PDF page 11) · source

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In our words: Serum 25(OH)D: below 16 ng/mL (40 nmol/L) is under the level that meets about half the population's needs; 16 to under 20 ng/mL is under the level that meets nearly everyone's needs; 20 to 50 ng/mL meets nearly everyone's needs; above 50 ng/mL (125 nmol/L) may carry a risk of harm.

Institute of Medicine committee (J Clin Endocrinol Metab 2011;96:53-58, doi:10.1210/jc.2010-2704) (2011) · Section 'Serum 25OHD Levels and Screening' · source

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In our words: A lactate above 2 mmol/L (18 mg/dL) is the lactate part of the septic-shock criteria; it never establishes septic shock on its own.

Society of Critical Care Medicine and European Society of Intensive Care Medicine task force (JAMA 2016;315:801-810) (2016) · Box 3 'New Terms and Definitions' · source

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In our words: Serum potassium (adults): 5.5 to 5.9 mmol/L mild; 6.0 to 6.4 moderate; 6.5 or higher severe.

UK Kidney Association (2026) · Introduction, document page 9 (PDF page 10) · source

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In our words: Bone density T-score (postmenopausal women): -1 or higher normal; between -1 and -2.5 low bone mass; -2.5 or lower osteoporosis; below -2.5 with a fragility fracture severe osteoporosis.

World Health Organization (1994) · Section 2.1 Definitions, printed pages 5-6 (PDF pages 11-12) · source

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In our words: Ferritin suggesting iron deficiency: below 15 µg/L at 5 years and older (healthy) and in first-trimester pregnancy; below 12 µg/L under 5 years (healthy); below 30 µg/L under 5 with infection or inflammation; below 70 µg/L at 5 and older with infection or inflammation.

World Health Organization (2020) · Executive summary, recommendations 1.1-1.2 (PDF page 11) and Table 1 (PDF page 12) · source

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In our words: Haemoglobin, adults 15 to 65, adjusted for altitude and smoking: anaemia below 130 g/L in men and below 120 g/L in non-pregnant women; moderate below 110 g/L; severe below 80 g/L. Pregnancy by trimester and children have their own cut-offs.

World Health Organization (2024) · Executive summary: Table 2 (PDF page 12), Table 3 (PDF page 13), Table 4 (PDF page 14), Table 5 (PDF page 15) · source

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