What laboratory tests are recommended for a competitive runner?

Laboratory Testing for Competitive Runners

For routine pre-participation screening of competitive runners, obtain a lipid profile (total cholesterol, HDL, triglycerides), fasting glucose, electrolytes, hemoglobin, and urinary protein by dipstick, with a 12-lead ECG recommended but not mandated. 1

Core Laboratory Panel

The American Heart Association and American College of Cardiology recommend the following baseline tests for all competitive athletes: 1

• Lipid profile: Total cholesterol, HDL cholesterol, and serum triglycerides 1
• Fasting glucose: Ideally after at least 9 hours of fasting, though if logistically difficult, can be obtained when convenient and repeated fasting only if abnormal 1
• Electrolytes: Serum electrolytes to assess baseline status 1
• Hemoglobin: To evaluate for anemia or hematologic abnormalities 1
• Urinary protein: Estimated by dipstick to screen for chronic renal disease, which is often asymptomatic until later stages and particularly common among young Black men 1

Blood Pressure Assessment

• Brachial artery blood pressure measurement is mandatory as part of the pre-participation evaluation 1
• If hypertension is identified (BP ≥140/90 mmHg), the above laboratory panel becomes even more critical for assessing cardiovascular risk factors and target-organ damage 1

Electrocardiogram Considerations

• A 12-lead ECG is recommended but not mandated for pre-participation screening 1
• The ECG helps identify left ventricular hypertrophy (LVH) or conduction abnormalities, though the yield is small in asymptomatic athletes 1
• For athletes with stage 2 hypertension (systolic BP >160 mmHg or diastolic BP >100 mmHg) or suggestions of target-organ damage, a screening echocardiogram is advisable to distinguish physiological athletic hypertrophy from pathological LVH 1

Additional Testing for Specific Scenarios

For Hypertensive Athletes

If classified as hypertensive, additional evaluation should include: 1

• Thyroid function tests (particularly if atrial fibrillation is suspected) 1
• Assessment for secondary causes of hypertension through history (family history, symptoms of pheochromocytoma, medication use including NSAIDs or stimulants) 1
• Physical examination for clues to secondary hypertension (abdominal bruits, cushingoid features) 1

For Athletes with Arrhythmias

If supraventricular or ventricular arrhythmias are detected: 1

• Thyroid function tests 1
• Echocardiogram 1
• Exercise stress test to assess arrhythmia behavior during exertion 1

Important Caveats for Interpreting Runner Laboratory Values

Expected Abnormalities in Distance Runners

Be aware that certain laboratory values may appear "abnormal" on routine clinical evaluation but are actually normal for elite runners: 2, 3

• Hematocrit may be classified as abnormally low due to expanded plasma volume ("sports anemia"), though true RBC deficiency is rare 2, 4
• Post-race metabolic derangements are common and include: 5, 3
  • Hyponatremia (8.2% prevalence post-race) 5
  • Renal dysfunction (42.6% post-race, with 45.8% classified as moderate or severe) 5
  • Elevated muscle enzymes (CK, AST, ALT) from exertional rhabdomyolysis 3
  • Elevated cardiac markers (CK-MB, myoglobin) without true cardiac injury 3
  • Increased bilirubin from hemolysis 3

Timing Considerations

• Avoid testing immediately post-race or post-training as values will be significantly altered by acute exercise effects 3
• If testing must occur post-exercise, interpret with modified reference ranges appropriate for marathon runners 3
• Pre-race testing may still show abnormalities (5% hyponatremia prevalence, 8.7% renal dysfunction) 5

Follow-Up Testing Schedule

• Initial comprehensive screening before beginning competitive athletics 1
• Repeat complete evaluation after 2 years for high school athletes 1
• College athletes: Complete history and physical on matriculation, then interim history annually with blood pressure measurement each of the subsequent 3 years 1
• Athletes with hypertension: Blood pressure monitoring every 2-4 months (or more frequently if indicated) 1

What NOT to Routinely Order

The American Heart Association panel does not recommend routine use of echocardiography for mass screening due to: 1

• Low prevalence of cardiovascular conditions causing sports-related deaths
• Limited resources and lack of available physician-examiners
• High false-positive rates that would create unnecessary anxiety and unjustified exclusions 1

However, echocardiography remains appropriate for individual athletes with specific clinical indications (stage 2 hypertension, symptoms, abnormal ECG with concerning features) 1