What is a comprehensive list of laboratory diagnostics and their indications?

Comprehensive List of Laboratory Diagnostics with Indications

A systematic approach to laboratory testing should prioritize targeted diagnostics based on clinical suspicion rather than ordering panels routinely, as this maximizes diagnostic yield while minimizing unnecessary testing.

Hematology Tests

Complete Blood Count (CBC) with Differential

• Indications: Baseline evaluation for virtually all conditions, screening for anemia, infection, inflammation, hematologic malignancies 1
• Components: Hemoglobin, hematocrit, RBC count, WBC count with differential, platelet count, RBC indices
• Special considerations: Essential for initial workup of leukemia, lymphoma, and monitoring chemotherapy 1

Peripheral Blood Smear

• Indications: Evaluation of abnormal CBC findings, suspected hematologic disorders, parasitic infections 1
• Special considerations: Critical for morphologic assessment in leukemia and other hematologic malignancies

Coagulation Studies

• Indications: Bleeding disorders, preoperative evaluation, monitoring anticoagulation therapy 1
• Components: Prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, D-dimer
• Special considerations: Essential for disseminated intravascular coagulation (DIC) panel 1

Chemistry Tests

Comprehensive Metabolic Panel

• Indications: General health screening, monitoring organ function, medication effects 1
• Components:
  • Electrolytes (sodium, potassium, chloride, bicarbonate)
  • Renal function (BUN, creatinine, eGFR)
  • Liver function (ALT, AST, alkaline phosphatase, bilirubin)
  • Glucose, calcium, albumin, total protein

Cardiac Biomarkers

• Indications: Suspected myocardial infarction, heart failure, cardiac stress 1
• Components: Troponin, CK-MB, BNP/NT-proBNP, high-sensitivity CRP
• Special considerations: Serial measurements often required for diagnosis of acute coronary syndrome

Lipid Profile

• Indications: Cardiovascular risk assessment, monitoring lipid-lowering therapy 1, 2
• Components: Total cholesterol, LDL, HDL, triglycerides
• Special considerations: Fasting may be required for accurate triglyceride measurement

Tumor Lysis Syndrome Panel

• Indications: Patients with high tumor burden, particularly before and during chemotherapy 1
• Components: Serum lactate dehydrogenase, uric acid, potassium, phosphates, calcium 1

Endocrine Tests

Thyroid Function Tests

• Indications: Suspected hypo/hyperthyroidism, monitoring thyroid replacement therapy 1, 2
• Components: TSH, free T4, free T3 (when indicated)
• Special considerations: TSH is the most sensitive initial test for primary thyroid disorders

Diabetes-Related Tests

• Indications: Screening and diagnosis of diabetes, monitoring glycemic control 1, 2
• Components: Fasting glucose, HbA1c, glucose tolerance test
• Special considerations: HbA1c reflects average glucose over 2-3 months

Immunology and Serology Tests

Autoimmune Panels

• Indications: Suspected autoimmune disorders, unexplained systemic symptoms 1
• Components: ANA, RF, anti-CCP, ANCA, anti-dsDNA based on clinical suspicion
• Special considerations: Testing should be guided by specific clinical features rather than ordered as complete panels

Immunoglobulin Studies

• Indications: Suspected immunodeficiency, monoclonal gammopathies, multiple myeloma 1
• Components: Serum quantitative immunoglobulins (IgG, IgA, IgM), serum protein electrophoresis (SPEP), serum immunofixation electrophoresis (SIFE) 1
• Special considerations: Essential for diagnosis of Waldenström macroglobulinemia and multiple myeloma

Infectious Disease Tests

Microbiology Studies

• Indications: Suspected infections, fever of unknown origin, immunocompromised patients 1
• Components: Blood cultures, urine cultures, wound cultures, stool cultures
• Special considerations: Collection before antibiotic administration is crucial

Serologic Testing

• Indications: Suspected viral, bacterial, or parasitic infections 1
• Components: HIV, hepatitis panels, Lyme disease serology, etc.
• Special considerations: Consider regional endemic diseases when ordering

Molecular Diagnostic Tests

• Indications: Rapid identification of pathogens, detection of antimicrobial resistance 1
• Components: PCR, nucleic acid amplification tests (NAATs)
• Special considerations: NAATs have high sensitivity but may detect colonization rather than active infection in some cases (e.g., C. difficile) 1

Specialized Tests

Genetic Testing

• Indications: Suspected hereditary disorders, pharmacogenomics, cancer risk assessment 1
• Components: Cytogenetics, FISH, molecular testing for specific mutations
• Special considerations: Essential for classification and risk stratification in hematologic malignancies 1

Bone Marrow Studies

• Indications: Unexplained cytopenias, suspected hematologic malignancies 1
• Components: Aspirate and biopsy with immunohistochemistry, flow cytometry, cytogenetics
• Special considerations: Critical for diagnosis of leukemia, lymphoma, multiple myeloma 1

Cerebrospinal Fluid Analysis

• Indications: Suspected meningitis, encephalitis, CNS malignancies 1
• Components: Cell count with differential, protein, glucose, cultures, cytology
• Special considerations: Essential for diagnosis of CNS involvement in leukemia/lymphoma

Disease-Specific Testing Algorithms

Hematologic Malignancy Workup

1. CBC with differential and peripheral blood smear
2. Bone marrow aspirate and biopsy with immunohistochemistry
3. Flow cytometry for immunophenotyping
4. Cytogenetics and molecular testing for specific mutations 1
5. Serum protein electrophoresis and immunofixation (for plasma cell disorders) 1

Heart Failure Evaluation

1. BNP or NT-proBNP
2. Cardiac troponins
3. Complete blood count
4. Comprehensive metabolic panel
5. Thyroid function tests 1

Eosinophilia Workup

1. CBC with differential and peripheral blood smear
2. Comprehensive metabolic panel with uric acid
3. Serum tryptase and vitamin B12 levels
4. Serum quantitative immunoglobulins including IgE
5. Consider parasitic infection testing based on exposure history 1

Common Pitfalls in Laboratory Testing

1. Overreliance on panels: Order tests based on specific clinical questions rather than using broad panels 2
2. Pre-analytical errors: Proper specimen collection, handling, and patient identification are critical to avoid errors 3
3. Failure to consider timing: Some tests require specific timing (fasting, diurnal variation, relation to medication administration)
4. Misinterpretation of results: Laboratory values must be interpreted in clinical context, considering sensitivity, specificity, and predictive values 4
5. Missing follow-up: Serial testing is often more informative than single measurements

Remember that laboratory testing should be guided by clinical suspicion rather than ordered routinely, with first-line tests tailored to the specific clinical scenario 2.