What are the blood testing biomarkers and optimal ranges for a general adult population?

Blood Testing Biomarkers and Optimal Ranges for General Adult Population

For general adult health screening, the most essential blood biomarkers include metabolic markers (glucose/HbA1c, lipid panel), liver function tests (ALT, AST, ALP, GGT, bilirubin, albumin), kidney function (creatinine/eGFR), complete blood count, and inflammatory markers (CRP), with specific optimal ranges varying by age, sex, and individual risk factors. 1

Core Metabolic Screening

Diabetes and Prediabetes Markers

• Fasting plasma glucose should be measured as the preferred initial test, with normal values <100 mg/dL, prediabetes 100-125 mg/dL (IFG), and diabetes ≥126 mg/dL 1
• Hemoglobin A1C serves as an equally appropriate alternative, with normal <5.7%, prediabetes 5.7-6.4%, and diabetes ≥6.5% 1, 2
• Testing should begin at age 35 years for all adults, or earlier (any age) in those with BMI ≥25 kg/m² (≥23 kg/m² in Asian Americans) plus any additional risk factor 1
• Repeat testing intervals: every 3 years minimum if normal; annually if prediabetes is identified 1, 2

Lipid Panel Components

• Total cholesterol, LDL, HDL, and triglycerides should be measured together as a comprehensive lipid profile 2
• HDL cholesterol <35 mg/dL (0.90 mmol/L) and/or triglycerides >250 mg/dL (2.82 mmol/L) indicate increased cardiovascular risk requiring intervention 1
• Lipid stability over 4-12 years ranges from 0.65 to 0.37, similar to blood pressure stability, supporting repeat measurement every 4-6 years in healthy adults starting at age 20 1

Liver Function Assessment

Standard Liver Panel

• Initial liver investigation must include bilirubin, albumin, ALT, ALP, and GGT, together with full blood count 1
• Abnormal results (outside laboratory reference range) warrant investigation regardless of the degree of elevation 1
• The pattern of elevation (hepatocellular vs. cholestatic) guides subsequent diagnostic workup 1

Liver Aetiology Screen Components

• Standard adult screen should include: abdominal ultrasound, hepatitis B surface antigen, hepatitis C antibody with reflex PCR, anti-mitochondrial antibody, anti-smooth muscle antibody, antinuclear antibody, serum immunoglobulins, simultaneous ferritin and transferrin saturation 1
• For suspected NAFLD with metabolic syndrome, risk stratification using FIB-4 or NAFLD Fibrosis Score should be incorporated into primary care systems 1

Kidney Function and Anemia Markers

Renal Function Assessment

• eGFR provides the most accurate assessment of kidney function, with stages defined as: Stage 1 (≥90 mL/min/1.73 m²), Stage 2 (60-89), Stage 3 (30-59), Stage 4 (15-29), Stage 5 (<15) 1
• Anemia prevalence increases significantly when eGFR falls below 60 mL/min/1.73 m² (Stage 3 CKD) 1

Hemoglobin Optimal Ranges

• Males: Hemoglobin <13.0 g/dL defines anemia 1
• Females: Hemoglobin <12.0 g/dL defines anemia 1, 3
• Mean hemoglobin levels decrease consistently only when GFR drops below 60 mL/min/1.73 m² 1
• Patients with diabetes develop anemia 2-3 times more frequently at all GFR levels compared to non-diabetics 1

Iron Studies for Anemia Evaluation

• Complete iron panel should include ferritin, transferrin saturation, serum iron, and total iron-binding capacity (TIBC) 3
• Low ferritin, low transferrin saturation, low iron, raised TIBC, and increased serum transferrin receptor indicate iron deficiency 3
• Iron deficiency without anemia is a recognized clinical entity requiring investigation and treatment 3

Cardiovascular and Inflammatory Biomarkers

High-Sensitivity C-Reactive Protein (CRP)

• CRP demonstrates strong stability over intervals <6 months (correlation ~0.79), modest to moderate stability over 6 months to 3 years, and lower stability over periods >3 years 1
• Two measurements taken 2 weeks apart are recommended to determine 10-year CHD risk, though repeat assessment every 1-3 years may be necessary for accurate risk prediction 1
• CRP stability estimates (0.65-0.88 over 6 months to 1 year) approximate those of blood pressure and lipid levels over similar periods 1

Cardiac Biomarkers for Risk Stratification

• High-sensitivity cardiac troponin T (hs-cTnT) and NT-proBNP identify individuals with elevated blood pressure or hypertension at highest risk for cardiovascular events and heart failure 1
• These biomarkers detect chronic myocardial injury and stress, identifying intermediate phenotypes along the progression from hypertension to clinical heart failure 1
• Elevated biomarker levels can identify individuals with stage 1 hypertension (BP 130-139/80-89 mmHg) who may benefit from antihypertensive medication beyond traditional risk assessment 1

Interleukin-6 (IL-6)

• IL-6 stability mirrors CRP, with strong stability <6 months, modest stability 6 months to 3 years 1
• IL-6 independently classifies clinical CVD and predicts all-cause mortality in high-risk populations, demonstrating robustness as a prognostic biomarker 4
• Repeated measurement every 6 months to 3 years may be necessary to accurately characterize health risk 1

Blood Pressure Assessment

• Hypertension threshold per 2017 ACC/AHA guidelines: ≥130/80 mmHg 1
• Clinical guidelines recommend reassessment every 1-2 years for healthy adults 1
• Blood pressure stability over 2-12 years ranges from 0.61 to 0.35 for systolic BP, with slightly lower estimates for diastolic BP 1

Testing Frequency and Stability Considerations

General Principles for Biomarker Monitoring

• Single measurements of most inflammatory biomarkers provide reliable indices of stable individual differences in the short term (<6 months) 1
• Repeated assessments are necessary over intervals >6 months to accurately estimate future health risk, with measurements repeated at minimum every 3 years 1
• Momentary exposures (acute stress, pollution) impact circulating levels, so repeated measurement in the short term (days to weeks) may provide more accurate measures of individual differences 1

Biomarker Variability Factors

• Most biomarkers demonstrate heterogeneity due to between-subjects factors (age, sex, fasting state) rather than analytic factors (assay differences) 1
• Diurnal variation and inter-/intravariability in assays must be considered when interpreting results 5
• Dynamic nature of risk in real-world settings (aging, incident risk factors) may affect biomarker interpretation over time 5

Common Pitfalls to Avoid

• Do not delay diabetes screening until age 35 in patients with BMI ≥25 kg/m² who have additional risk factors; severe obesity (BMI ≥40 kg/m²) qualifies as high-risk requiring immediate screening 1, 2
• Do not use A1C in conditions with altered red blood cell turnover (hemolytic anemia, recent blood loss); use only glucose-based criteria in these situations 1, 2
• Do not interpret liver tests in isolation; always review previous results, past medical history, and current clinical context before determining significance 1
• Do not assume normal hemoglobin excludes iron deficiency; iron deficiency can cause symptoms even before hemoglobin drops below normal thresholds 3
• Do not rely on single biomarker measurements for long-term risk prediction; inflammatory markers require repeat testing every 3 years minimum to maintain accuracy 1