Florence Test
Definition
Presumptive semen test. Iodine plus potassium iodide reacts with choline in semen to form dark-brown rhombic / needle-shaped choline iodide crystals.
- Type
- Presumptive semen test
- Reagent
- Iodine and potassium iodide
- Target
- Choline
- Positive result
- Dark-brown rhombic or needle-shaped choline iodide crystals
Common questions
Why is the Florence test called presumptive rather than confirmatory?+
Choline occurs in body fluids and secretions other than semen, so a positive crystal reaction indicates the presence of choline but does not on its own prove seminal origin. A confirmatory test, such as identifying spermatozoa or a semen-specific protein, is needed before the result is treated as conclusive.
What can cause a false negative on the Florence test for an actual semen stain?+
Low choline concentration from an aged, degraded, or very dilute stain, or from an azoospermic sample, can fail to produce visible crystals even though seminal material is genuinely present, which is why a negative result does not rule out semen either.
Related terms
- Acid Phosphatase (AP)
- An enzyme present at high concentrations in seminal plasma. The Brentamine Fast Violet B (or SERI AP) spray test detects acid phosphatase...
- Alpha-Amylase
- Salivary enzyme. Detected by starch-iodine (clear zone in blue background) or the Phadebas reagent (blue colour from dye-linked starch). Concentration in saliva...
- Barberio Test
- Presumptive semen test. Saturated picric acid reacts with spermine to form yellow rhombic spermine picrate crystals.
- Hp, Gc, Tf
- The classical serum-protein polymorphism panel: haptoglobin (binds free haemoglobin; Hp1-1, Hp2-1, Hp2-2 phenotypes), group-specific component (vitamin D binding protein, Gc1F / Gc1S...
- Isoenzyme / Polymorphism
- Different molecular forms of the same enzyme separable by electrophoresis. Forensic polymorphic markers have several common alleles in the population, so a...
- P30 (PSA)
- Prostate-specific antigen, a glycoprotein secreted by the male prostate gland and present in semen at high concentrations. ELISA or lateral-flow immunochromatographic tests...
- PGM, EsD, AK, GLO
- The classical RBC isoenzyme panel: phosphoglucomutase, esterase D, adenylate kinase, glyoxalase I. All polymorphic, all typed by starch-gel or isoelectric-focusing electrophoresis of...
- Secretor
- An individual whose ABO blood group antigens are expressed on red blood cells and also released into body fluids such as saliva,...
- Spermatozoa
- Mature male gametes. Microscopic identification of intact spermatozoa with the characteristic head, midpiece and tail is the gold-standard confirmatory for semen in...