The initial evaluation of patients with small cell lung cancer (SCLC) confirmed by histopathological findings include a complete blood count with differential, electrolytes, liver function test, calcium level, LDH, BUN, and creatinine. These laboratory tests should also be performed to assess the response to the initial therapy.

The following laboratory tests must be ordered in all patients with SCLC during the initial evaluation as well as during the assessment of response to treatment following the initial therapy:^[1]

• Complete blood count with differential
  • Low hemoglobin, thrombocytopenia, or leukopenia can be found if the metastatic cells infiltrated the bone marrow.
• Electrolytes
  • Hyponatremia can be present if syndrome of inappropriate antidiuretic hormone secretion (SIADH) occurred as a complication of SCLC.
• Liver function test
  • Liver function test should be done as a baseline and will be monitored during treatment. Liver enzymes can be elevated in metastasis.
• Calcium level
  • Hypercalcemia can be present in case of excessive production of parathyroid hormone as a paraneoplastic syndrome.
• BUN
• Creatinine
• LDH

• Detection of tumor markers may allow the cancer to be detected at an early stage and may change the outlook of the disease.
• The following tumor markers have been found to be associated with small cell lung cancer:

• • Chromogranin A (CgA)
  • Pro-gastrin releasing peptide (ProGRP)
  • Neuron-specific enolase (NSE; an γ-γ isoform of the ubiquitous enolase enzyme)
  • Cytokeratin 19

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