What lab tests should be run for a patient with Sarcoidosis?

Laboratory Testing for Sarcoidosis

All patients with sarcoidosis should undergo baseline laboratory testing including serum calcium, serum creatinine, serum alkaline phosphatase, complete blood count, and ECG to screen for organ involvement and complications. 1

Essential Baseline Laboratory Tests

Calcium Metabolism Screening

• Serum calcium is strongly recommended for all patients with sarcoidosis, even without symptoms or signs of hypercalcemia, to screen for abnormal calcium metabolism 2, 1
• If vitamin D assessment is needed (e.g., to determine if replacement is indicated), measure both 25-OH and 1,25-OH vitamin D levels before any supplementation 2, 1
  • This is critical because sarcoid granulomas produce excess 1α-hydroxylase, converting 25-OH to 1,25-OH vitamin D, which can worsen hypercalcemia 3

Renal Function Assessment

• Serum creatinine should be measured to screen for renal involvement, as hypercalcemia can cause renal insufficiency in 42% of untreated patients 1, 3

Hepatic Function Assessment

• Serum alkaline phosphatase should be measured to screen for hepatic sarcoidosis 1, 3
• Alkaline phosphatase greater than three times the upper limit of normal is considered probable for sarcoidosis involvement 2

Hematologic Assessment

• Complete blood count (CBC) is recommended to screen for hematologic abnormalities 2, 3
• Anemia occurs in 22% of patients, and lymphopenia ranges from 27-55% 2
• These abnormalities may indicate bone marrow involvement, splenic sequestration, or compartmentalization of white blood cells to sites of organ involvement 2

Cardiac Screening Tests

Electrocardiogram

• Baseline ECG is strongly recommended for all patients with sarcoidosis, even without cardiac symptoms, to screen for cardiac involvement 4, 1, 3
• This is critical because cardiac sarcoidosis can be fatal and is present in 25% of patients but only causes clinical problems in 5% 5

Advanced Cardiac Testing (When Indicated)

• Do NOT perform routine echocardiography or 24-hour Holter monitoring in asymptomatic patients with normal ECG 4, 3
• If ECG shows abnormalities or cardiac symptoms are present, cardiac MRI is the preferred first-line imaging modality 4, 1, 3
• If cardiac MRI is unavailable, use dedicated PET scanning rather than echocardiography 4, 3

Optional or Adjunctive Tests

Angiotensin-Converting Enzyme (ACE)

• ACE levels lack sensitivity and specificity and should not be relied upon solely for diagnosis 1
• However, ACE elevated above 50% of the upper limit of normal may support the diagnosis when combined with other clinical features 2
• ACE levels may correlate with calcium levels and can be used as a marker of disease activity 3, 6

Bronchoalveolar Lavage (BAL)

• BAL showing lymphocytosis or elevated CD4:CD8 ratio is considered probable for sarcoidosis 2
• This is typically obtained during bronchoscopy when tissue diagnosis is needed 1

Common Pitfalls to Avoid

• Do not rely solely on ACE levels for diagnosis or monitoring, as they have poor diagnostic accuracy 1
• Do not supplement vitamin D without first measuring both 25-OH and 1,25-OH levels, as this can worsen hypercalcemia in sarcoidosis patients 2, 3
• Do not skip cardiac screening with ECG, even in asymptomatic patients, as cardiac involvement can be life-threatening 4, 1, 5
• Do not perform routine advanced cardiac imaging (echocardiography, Holter monitoring) unless ECG is abnormal or symptoms are present 4, 3

Additional Testing Based on Organ Involvement

• Ophthalmology referral for baseline eye exam to screen for uveitis, which may be asymptomatic but can cause permanent vision impairment 1, 5
• 24-hour urine calcium may be considered if abnormal calcium metabolism is suspected, though serum calcium is the primary screening test 2
• Pulmonary function tests are essential for staging pulmonary disease severity and monitoring response to therapy 6, 7