Guide to laboratory tests

How to use this guide

This guide explains what each group of tests measures. It is not a recommendation to do them all. The doctor chooses tests according to symptoms, age and risk — see How tests are chosen and interpreted.

Hematology

• Complete blood count with differential — red cells, hemoglobin, white cells and platelets. Detects anemia, infections and other disorders.
• Peripheral blood smear — looking at the cells under a microscope, when the blood count shows changes.
• Erythrocyte sedimentation rate (ESR) and CRP (C-reactive protein) — non-specific markers of inflammation; they do not show which disease it is.

Glucose and metabolism

• Fasting glucose and HbA1c (average blood glucose over the last 2–3 months) — for diagnosing and monitoring diabetes.
• Glucose tolerance test (50, 75 or 100 g) — there are different protocols, especially in pregnancy; they are not interchangeable alternatives.
• Insulin, C-peptide, HOMA-IR — as indicated; HOMA-IR is not a universal screening test.

Kidneys and electrolytes

Creatinine with eGFR, urea, uric acid, sodium, potassium, chloride, calcium, magnesium. See Kidney function tests.

Liver and pancreas

ALT, AST, ALP, GGT, bilirubin, albumin, total protein — for the liver and bile ducts. Amylase and lipase — for the pancreas, when there is clinical suspicion.

Lipids

Total cholesterol, LDL, HDL, triglycerides; in selected cases Lp(a) and apolipoprotein B. See High cholesterol.

Thyroid

• TSH and FT4 — the main function tests.
• FT3 — when there is a specific indication.
• Anti-TPO, anti-Tg, TSH receptor antibodies (TRAb) — for autoimmune diseases (Hashimoto's, Graves').
• Thyroglobulin and calcitonin — specific indications, not routine checks.

Iron and vitamins

• Ferritin — iron reserves; it can also rise with inflammation.
• Serum iron, transferrin.
• Vitamin B12, folate, vitamin D (25-OH) — when there is a clinical reason.

Coagulation

• PT/INR, aPTT, fibrinogen — assess clotting; INR is used to monitor warfarin.
• D-dimer — used in certain algorithms when thrombosis is suspected; a raised value does not by itself confirm thrombosis.
• Thrombophilia panel (antithrombin, protein C and S, antiphospholipid antibodies) — only in selected cases, not after every thrombosis.

Immunology and autoimmunity

ANA, anti-dsDNA, ENA, rheumatoid factor, anti-CCP, HLA-B27 — interpreted only according to clinical suspicion. A positive result does not automatically mean autoimmune disease. ASO shows a past streptococcal infection but does not diagnose acute pharyngitis.

Celiac disease

• First-line test: anti-tissue transglutaminase IgA (tTG-IgA) together with total IgA.
• Keep eating gluten until the work-up is complete — removing it makes the test inaccurate.

Infectious serology

• Hepatitis B: HBsAg, anti-HBs, anti-HBc. See Hepatitis B.
• Hepatitis C: anti-HCV antibody; if positive, it is confirmed with HCV-RNA.
• HIV: combined antigen/antibody test, followed by a confirmatory test.
• Rubella, CMV, toxoplasma — especially before or during pregnancy, with specialist interpretation.
• Herpes: HSV IgM is not recommended; for active lesions, direct testing of the lesion is preferred.
• Typhoid fever: the Widal test is not reliable as the only proof.

Microbiology

Urine culture, blood culture, stool culture, wound and secretion cultures — according to the site of infection. The antibiogram shows which antibiotics work.

For genital infections: chlamydia and gonorrhea are tested by a molecular method (NAAT), not by an ordinary vaginal culture. Mycoplasma genitalium has specific indications.

H. pylori: stool antigen or breath test. FIT (fecal occult blood): a test for colorectal screening.

Tumor markers

CEA, CA 15-3, CA 125, CA 19-9, AFP, HE4, PSA — for specific diagnostic or follow-up contexts. They are not a package to rule out cancer in people without symptoms. The decision on PSA requires a discussion with the doctor about the benefits and limitations. See CA 15-3.

Hormones

• Reproductive: FSH, LH, estradiol, progesterone, prolactin, testosterone, AMH — the day of the cycle, the time of day and medicines affect the result. AMH does not by itself predict the chance of pregnancy.
• Adrenal and pituitary: ACTH, cortisol, IGF-1 — often with dynamic protocols.

Genetics and molecular tests

Karyotype, thalassemia tests, BRCA1/2 and others require an indication and usually genetic counselling. Non-invasive prenatal tests (NIPT) are screening tests, not a definitive diagnosis — a positive result needs confirmation.

Drug monitoring

The level of some drugs (e.g. valproate, carbamazepine, digoxin, tacrolimus) is measured at a specific time in relation to the dose. Ask about the timing before having blood drawn.