287 articles
Placental Function Tests
Placental function tests assess placental health in pregnancy via maternal biochemistry (oestriol, hPL, PlGF), uterine and umbilical artery Doppler, and ultrasound. Cochrane evidence shows biochemical tests alone do not improve pregnancy outcomes; Doppler benefits high-risk pregnancies.
Plasma osmolality
Plasma osmolality (serum osmolality) is the concentration of osmotically active particles in plasma, normally 275-295 mOsm/kg, measured by freezing point osmometry; the osmolal gap screens for toxic alcohols.
Platelet aggregometry
Platelet aggregometry is a family of laboratory tests that measures platelet clumping in blood samples, usually after adding an agonist such as ADP or collagen, to diagnose platelet function disorders.
Platelet function testing
Platelet function testing, also called platelet function tests, is a group of laboratory assays measuring platelet aggregation and activation to diagnose bleeding disorders and monitor antiplatelet drug effects.
Point-of-care testing
Point-of-care testing (POCT, near-patient testing) is clinical laboratory testing performed at or near the patient, typically with ~15-minute turnaround via lateral flow immunoassays and molecular platforms, governed in the US by CLIA waived-test rules.
Pooled testing
Pooled testing combines specimens from several people into one diagnostic test, clearing many with a single negative result and saving tests when infection is rare.
Positive occult blood in stool
Positive occult blood in stool: a fecal occult blood test (FOBT, gFOBT, or FIT) has found hidden blood, signaling digestive tract bleeding from hemorrhoids, polyps, ulcers, or colorectal cancer; colonoscopy follow-up is standard.
Precipitin Tests
Precipitin tests are serologic assays in which soluble antigen and homologous antibody form a visible precipitate. Introduced by Kraus in 1897 and applied forensically by Uhlenhuth in 1901, they identify species origin of bloodstains and quantify antibody.
Predictive testing
Predictive testing is genetic testing of an asymptomatic person to estimate their risk of a hereditary disease later in life, first applied to Huntington disease in 1987 and always paired with counseling.
Pregnancy test
Pregnancy test: home or clinical qualitative immunoassay detecting human chorionic gonadotropin (hCG) in urine; most reliable from the first day of a missed period, with brand accuracy varying widely from packaging claims.
Preimplantation genetic screening
Preimplantation genetic screening, now called PGT-A, is a reproductive medicine procedure that tests IVF embryos for chromosomal abnormalities before transfer, selecting embryos most likely to produce a live birth.
Preimplantation genetic testing
Preimplantation genetic testing (PGT) is a reproductive medicine procedure that analyzes IVF embryos for genetic or chromosomal abnormalities before transfer, divided into PGT-A, PGT-M, and PGT-SR.
Prenatal testing
Prenatal testing: screening (first-trimester combined, quad screen, cfDNA/NIPT) and diagnostic (CVS, amniocentesis) tests for fetal aneuploidy; cfDNA sensitivity ~99% for trisomy 21 but PPV depends on prevalence; procedure loss risk ~0.1-1%.
Presymptomatic testing
Presymptomatic testing is a genetic test on an asymptomatic person at family risk to determine whether they inherited a disease-causing mutation for a disorder that typically appears later in life.
Procalcitonin
Procalcitonin (PCT), the 116-amino acid prohormone of calcitonin, is a blood biomarker that rises in bacterial infection and sepsis, guides antibiotic start and stop decisions, and outperforms CRP diagnostically.
Prostate Health Index
The Prostate Health Index (phi) is a blood test combining three PSA forms into one score, used to estimate prostate cancer risk and reduce unnecessary biopsies.
Prostate specific antigen positive
Prostate specific antigen positive (ICD-11 MA14.1B) is the clinical finding of elevated blood PSA, a prostate-made protein raised by prostate cancer, benign prostatic hyperplasia, prostatitis, or recent procedures; it triggers repeat testing, MRI, and biopsy, not a cancer diagnosis.
Protein-to-creatinine ratio
The protein-to-creatinine ratio, validated in 1983, is a urine test that estimates 24-hour protein excretion from a single sample, with about 3.1 mg/mg indicating nephrotic-range proteinuria.
Provocation testing
Provocation testing is a diagnostic method in which a suspected trigger, such as a drug, food allergen, or hormone, is given in escalating doses under medical supervision to confirm hypersensitivity.
Prussian Blue Reaction
The Prussian blue reaction, also known as Perls' stain or the iron stain, is a histochemical technique that detects ferric iron in tissues, described by Max Perls in 1867.
PSA testing
PSA testing, also known as the PSA test, is a blood test measuring prostate-specific antigen to screen men for prostate cancer, though it carries risks of false positives and overdiagnosis.
Pulse oximetry
Pulse oximetry, invented by Takuo Aoyagi (1972/1974), non-invasively estimates arterial oxygen saturation (SpO2) and pulse rate via light through a fingertip; accuracy is reduced by poor perfusion and darker skin pigmentation, prompting FDA 2025 draft guidance.
Quest Diagnostics
Quest Diagnostics (NYSE: DGX), founded 1967 as MetPath by Paul Brown and spun off from Corning in 1997, is a Secaucus, New Jersey-based clinical laboratory company; with Labcorp it leads U.S. lab testing, with 2,000+ patient service centers and $3.04 billion Q2 2026 revenue.
Rapid diagnostic test
A rapid diagnostic test, or RDT, for malaria is a point-of-care immunochromatographic strip that detects Plasmodium antigens in finger-prick blood, giving results in about 15 to 30 minutes.
Reagent Strips
Reagent strips are chemically impregnated strips for detecting substances, chiefly urine dipsticks and blood glucose strips; history runs from Maumené's 1850 wool strip through Pavy and Oliver's 1880s dry chemistry to Clinistix (1956) and Multistix.
Reference ranges for blood tests
Reference ranges for blood tests (reference intervals) are the central 95% of values from healthy populations, defined by CLSI/IFCC EP28-A3c; they vary by laboratory, method, age, and sex, and harmonization efforts seek common intervals.
Reflex testing (laboratory medicine)
Reflex testing is a laboratory medicine practice in which a pre-determined result, such as a positive screen, automatically triggers confirmatory tests on the same specimen without a new physician order.
Residual disease testing
Residual disease testing, also called measurable or minimal residual disease (MRD) assessment, detects the few cancer cells that persist in blood or bone marrow after treatment, guiding relapse risk.
RET rearrangement analysis
RET rearrangement analysis is a molecular diagnostic test that detects RET gene fusions in tumors, most often papillary thyroid carcinoma and non-small-cell lung cancer, guiding treatment with selective RET inhibitors.
Rotational thromboelastometry
Rotational thromboelastometry (ROTEM) is a point-of-care viscoelastic test that measures clot formation, firmness, and lysis in whole blood, guiding hemostatic therapy in trauma, cardiac surgery, and obstetrics.