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Understand ALK fusion testing in lung cancer, including what a positive or negative result means, tissue and ctDNA methods, limitations, and treatment relevance.

ALK Fusion Test for Lung Cancer: Gene Fusion, Positive Result, and Molecular Meaning

Understand BRAF V600E testing in lung cancer, including what a positive or negative result means, tissue and ctDNA methods, limitations, and treatment relevance.

BRAF V600E Test for Lung Cancer: Mutation Status, Positive Result, and Molecular Meaning

Learn how the carcinoembryonic antigen (CEA) test is used in lung cancer, what high levels can mean, common non-cancer causes, reference ranges, and why serial trends matter.

CEA Test for Lung Cancer: Tumor Marker Monitoring, High Levels, and Result Meaning

Learn how the cytokeratin 19 fragment 21-1 (CYFRA 21-1) test is used in lung cancer, what high levels can mean, common non-cancer causes, reference ranges, and why serial trends matter.

CYFRA 21-1 Test for Lung Cancer: Tumor Marker Levels and Disease Monitoring

Understand EGFR exon 20 insertion testing in lung cancer, including what a positive or negative result means, tissue and ctDNA methods, limitations, and treatment relevance.

EGFR Exon 20 Insertion Test: Lung Cancer Mutation Status and Molecular Meaning

Understand EGFR mutation testing in lung cancer, including what a positive or negative result means, tissue and ctDNA methods, limitations, and treatment relevance.

EGFR Mutation Test for Lung Cancer: Exon 19, L858R, T790M, Mutation Status, and...

Diagnostics

Home Diagnostics Page 21

Learn what an IL-23 test measures, how the Th17 pathway affects autoimmune inflammation, why high or low results are limited, and how related diseases are evaluated.

Interleukin-23 (IL-23) Test: Autoimmune Inflammation, Th17 Pathway, and Meaning

Learn how lymphocyte proliferation tests measure T-cell division, why mitogen and antigen responses differ, what low results mean, and how specimen handling affects accuracy.

Lymphocyte Proliferation Test: T-Cell Function, Mitogen Response, and Immune Deficiency

Understand how a lymphocyte subset panel measures T, B, and NK cells, why absolute counts and percentages differ, and how CD4/CD8 patterns guide immune evaluation.

Lymphocyte Subset Panel: T Cells, B Cells, NK Cells, CD4/CD8 Ratio,...

Learn how a macrophage activation syndrome blood test panel uses ferritin, blood counts, fibrinogen, liver tests, IL-18, and cytokine markers to detect dangerous hyperinflammation.

Macrophage Activation Syndrome Blood Test Panel: Ferritin, IL-18, Cytokines, and Hyperinflammation

Understand what a natural killer cell count measures, why CD16 and CD56 identify NK cells, and how low or high results relate to viral defense, immune deficiency, treatment, and function.

Natural Killer Cell Count Test: NK Cells, Immune Function, and Viral...

Learn how natural killer cell function tests measure cytotoxicity, CD107a degranulation, perforin, and immune activity, and why specimen handling and clinical context determine the meaning.

Natural Killer Cell Function Test: NK Cell Activity, Immune Defense, and...

Learn how the neutrophil oxidative burst DHR test screens for chronic granulomatous disease, identifies carrier patterns, measures residual NADPH oxidase activity, and avoids false interpretation.

Neutrophil Oxidative Burst Test: Chronic Granulomatous Disease Screening and Neutrophil Function

Understand how regulatory T-cell testing measures CD4 CD25-high CD127-low FOXP3-positive cells, what low or high Tregs may mean, and why IPEX requires genetic confirmation.

Regulatory T-Cell Test: Tregs, Immune Tolerance, Autoimmunity, and Meaning

Understand what a soluble IL-2 receptor or sCD25 test measures, why levels rise in HLH, sarcoidosis, lymphoma, infection, and inflammation, and why the result is not disease-specific.

Soluble IL-2 Receptor Test: Immune Activation, Inflammation, Sarcoidosis, and Lymphoma Risk

Understand how a CD3 T-cell count measures circulating T lymphocytes, why absolute counts and percentages differ, and how low or high results guide immune-function and subset evaluation.

T-Cell Count Test: CD3 Cells, Immune Function, and Lymphocyte Subsets

Understand what a TGF-beta 1 blood test measures, why platelets and latent protein affect results, and why high levels cannot diagnose fibrosis, immune dysregulation, or cancer alone.

Transforming Growth Factor-Beta (TGF-Beta) Test: Immune Regulation, Fibrosis, and Meaning

Understand what a TNF-alpha blood test measures, why levels may be high or normal, major limitations, anti-TNF treatment differences, and appropriate follow-up.

Tumor Necrosis Factor-Alpha (TNF-Alpha) Test: High Levels, Inflammation, and Cytokine Activity

Learn what a VEGF blood test measures, why serum and plasma differ, how platelets affect results, its role in POEMS syndrome, and what high levels can mean.

Vascular Endothelial Growth Factor (VEGF) Test: Inflammation, Angiogenesis, and Blood Vessel...

Learn what the AH50 complement test measures, why low activity occurs, how AH50 and CH50 patterns identify pathway defects, and which follow-up tests may be needed.

AH50 Complement Test: Alternative Pathway Activity, Low Levels, and Immune Function

Understand what the C1 esterase inhibitor antigen test measures, how low levels support type I hereditary angioedema, and why function, C4, and C1q are needed for diagnosis.

C1 Esterase Inhibitor Antigen Test: Hereditary Angioedema, Low Levels, and Diagnosis

Learn how the C1 esterase inhibitor function test detects hereditary angioedema, how low and equivocal results are interpreted, and why antigen, C4, C1q, and repeat testing matter.

C1 Esterase Inhibitor Function Test: Hereditary Angioedema, Functional Deficiency, and Diagnosis

Learn what the CH50 complement test measures, why results may be low or high, how CH50 and AH50 patterns locate pathway defects, and which follow-up tests are commonly used.

CH50 Complement Test: Total Complement Activity, High and Low Levels, and...

Learn which tests are included in a CVID panel, how IgG, IgA, IgM, pneumococcal and protein vaccine responses are interpreted, and how secondary causes are excluded before diagnosis.

Common Variable Immunodeficiency Test Panel: IgG, IgA, IgM, Vaccine Response, and...

Understand what a C3, C4, CH50, IgG, IgA, and IgM panel measures, how common result patterns are interpreted, and which follow-up tests assess complement and antibody function.

Complement and Immunoglobulin Blood Test Panel: C3, C4, CH50, IgG, IgA,...

Understand what a low complement C1q test may mean, how C1q differs from anti-C1q antibodies, and how it fits into lupus nephritis and angioedema evaluation.

Complement C1q Test: Low Levels, Immune Complex Disease, and Lupus Nephritis...

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