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Learn how HLA-DR and CD38 flow cytometry measures activated T cells, what high results may mean, why ranges vary, and how clinicians plan follow-up.

Activated T-Cell Marker Test: HLA-DR, CD38, Immune Activation, and Inflammation

Understand how CD19 and CD20 B-cell counts are measured, why results may be high or low, how anti-CD20 therapy affects them, and which follow-up tests assess antibody function.

B-Cell Count Test: CD19, CD20, Immune Function, and Antibody Production

Learn what a CD4 count measures, how HIV affects helper T cells, what common ranges and thresholds mean, why results fluctuate, and how the test guides monitoring and infection prevention.

CD4 Count Test: Helper T Cells, Immune Function, HIV Monitoring, and Meaning

Learn how the CD4/CD8 ratio is calculated, what low or high results may mean, why an inverted ratio is nonspecific, and how the test adds context in HIV and immune monitoring.

CD4/CD8 Ratio Test: Immune Balance, High and Low Ratio, and Meaning

Learn what a CD8 count measures, why cytotoxic T-cell numbers may rise or fall, how viral infections affect results, and why cell quantity does not equal antiviral function.

CD8 Count Test: Cytotoxic T Cells, Immune Function, and Viral Response

Understand what a chemokine panel measures, why immune-signaling and cell-migration markers rise or fall, and how specialists interpret patterns and limitations.

Chemokine Panel Test: Immune Signaling, Inflammation, and Cell Migration Markers

Diagnostics

Home Diagnostics Page 17

Learn what a DHEA blood test measures, why levels may be high or low, how age and timing affect the normal range, and which adrenal hormone tests may come next.

DHEA Blood Test: High, Low, Normal Range, Adrenal Function, and Results

Understand what a DHEA-S blood test shows, normal ranges by age and sex, causes of high or low adrenal androgen levels, and the follow-up tests used to interpret results.

DHEA-S Blood Test: High, Low, Normal Range, Adrenal Androgens, and Results

Learn how the high-dose dexamethasone suppression test is used in ACTH-dependent Cushing syndrome, what 50% cortisol suppression means, and why other localization tests are often needed.

High-Dose Dexamethasone Suppression Test: Cushing Disease and Results

Learn how late-night cortisol screening detects loss of the normal cortisol rhythm, what high salivary results mean, common false positives, and which Cushing tests usually follow.

Late-Night Cortisol Test: High Levels, Cushing Syndrome Screening, and Results

Understand the 1-mg low-dose dexamethasone suppression test, the common cortisol cutoff of 1.8 mcg/dL, causes of nonsuppression, and the follow-up used for Cushing screening.

Low-Dose Dexamethasone Suppression Test: Cushing Syndrome Screening and Results

Learn how an 8–9 a.m. cortisol test screens for adrenal insufficiency, what low and intermediate results mean, how ACTH helps identify the cause, and when stimulation testing is needed.

Morning Cortisol Test: Low Levels, Adrenal Insufficiency, and Results

Learn how a pheochromocytoma and paraganglioma panel uses plasma or urine metanephrines, normetanephrine, catecholamines, and controlled collection to interpret abnormal results.

Pheochromocytoma and Paraganglioma Test Panel: Metanephrines, Normetanephrine, Catecholamines, and Results

Learn what plasma epinephrine, norepinephrine, and dopamine results mean, why collection posture matters, common causes of high values, and when metanephrine testing is preferred.

Plasma Catecholamines Test: Epinephrine, Norepinephrine, Dopamine, and Results

Learn how plasma free metanephrine and normetanephrine testing screens for pheochromocytoma and paraganglioma, why supine rest matters, and how high or borderline results are evaluated.

Plasma Free Metanephrines Test: Pheochromocytoma and Paraganglioma Screening, High Levels, and...

Learn what a high plasma normetanephrine result means, why supine rest matters, common false-positive causes, when clonidine testing is used, and how PPGL evaluation proceeds.

Plasma Normetanephrine Test: High Levels, Pheochromocytoma Screening, and Results

Learn how aldosterone, renin, potassium, and the ARR screen for primary aldosteronism, how medicines affect results, and when confirmation, CT, or adrenal vein sampling is needed.

Primary Aldosteronism Test Panel: Aldosterone, Renin, Potassium, ARR, and Results

Learn what high or low renin means, how PRA differs from direct renin, how aldosterone and potassium complete the pattern, and why medicines and posture affect the ARR.

Renin Blood Test: High, Low, Normal Range, Aldosterone Ratio, and Results

Learn how salivary cortisol reflects the daily rhythm, when late-night testing screens for Cushing syndrome, why stress panels have limits, and what high, low, or flat results may mean.

Salivary Cortisol Test: Cortisol Rhythm, Cushing Screening, Stress Hormone, and Results

Learn how a 24-hour urine catecholamines test measures epinephrine, norepinephrine, and dopamine, why collection quality matters, and when metanephrine testing is preferred.

Urine Catecholamines Test: Adrenal Tumor Screening and Results

Learn how 22q11.2 deletion syndrome genetic testing works, what positive, negative, prenatal, and family results mean, and which follow-up evaluations may be needed.

22q11.2 Deletion Syndrome Genetic Test: DiGeorge Syndrome and Results

Understand how amniocentesis tests fetal chromosomes and DNA, when it is offered, how the procedure works, what results mean, and the risks and alternatives.

Amniocentesis Genetic Test: Chromosomes, DNA, Diagnosis, and Results

Learn how cell-free DNA prenatal screening works, what low-chance, high-chance, no-call, and atypical results mean, and when CVS or amniocentesis is needed.

Cell-Free DNA (cfDNA) Prenatal Test: Fetal Chromosome Screening and Results

Learn how CFTR testing helps diagnose congenital absence of the vas deferens, how to read results, why partner testing matters, and which fertility options are available.

CFTR Genetic Test for Male Infertility: Congenital Absence of the Vas...

Learn how chorionic villus sampling provides early prenatal diagnosis, how CVS is performed, what normal, abnormal, uncertain, and mosaic results mean, and when amniocentesis may be needed.

Chorionic Villus Sampling (CVS) Genetic Test: Prenatal Diagnosis and Results

Understand Down syndrome genetic testing, including trisomy 21 screening, CVS and amniocentesis diagnosis, chromosome results, recurrence, and next steps.

Down Syndrome Genetic Test: Trisomy 21 Screening, Diagnosis, and Results

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