Serology Blood Lecture

serology blood

What is blood?

a fluid mostly made up of water that contains cells, platelets, various proteins and enzymes.

Where are blood cells produced?

Bone marrow

What is blood composed of?

45 % cells (erythrocytes, leukocytes & platelets)

55% Plasma (water, electrolytes, nutrients & proteins)

What are erythrocytes?

red blood cells. they don’t have a nucleus and are most abundant cells in blood. 120 days lifespan.

What is hemstocrit?

a measurement that gives the percentage of RBC in someone’s blood.

What molecule gives RBC it’s red color?

Hemoglobin, a protein that has 4 iron atom. Each iron binds to 2 oxygen.

What are white blood cells?

Leukocytes. Has a variable lifespan.

What are platelets?

Thrombocytes. Helps in blood clotting and has a lifespan of 10 days.

Forensic presumptive tests focuses on which part of the blood?

the iron of the hemoglobin

What is the presumptive blood test reaction?

Hemoglobin rxn with peroxide

Who was Christian F. Schonbein

a chemist who discovered catalytic oxidation or decomposition of hydrogen peroxide (H2O2) by living materials.

Who was Joseph Kastle?

discovered and tested the use of phenolphthalein as peroxidase indicator in 1901

who was Meyer

discovered the medical use for phenolphthalein.

what are blood presumptive tests?

• A test that shows the probability of blood.

• They are very sensitive, but not specific.

• Can give false +

examples of presumptive blood test:

Phenolphthalein

benzidine

tetramethalbenzidine

luminol

LGM

o-tolidine

which presumptive test are known to be safe?

phenolphthalein, LMG and Luminol

which presumptive test are known to be very sensitive?

Benzidine, tetramethylbenzidine, luminol

Why isn’t LMG used instead of phenolphthalein

it has a 24hrs shelf life

Which test displays a dark blue color during reaction?

benzidine, tetramethylbenzidine and o-tolidine.

Phenolphthalein rxn

reaction prep:

1. Stock solution: phenolphthalein + Potassium hydroxide + Zinc. (O2 is removed & combined with OH from KOH; its colorless.

2. Working solution: becomes phenolphthalin + ethanol + Zinc.

   • when reacted with a heme, ethanol lice’s cell and zinc prevents oxidation

What are the cautious measures to take with zinc?

it must be disposed appropriately, NOT TRASH. Can become a fire hazard when zinc dust or powder may heat spontaneously and ignite on exposure to air when damp.

How to perform 2 step rxn phenolphthalein test?

2 step process: the reagent is applied, then the oxidizer (sodium perborate).

what is luminol reaction?

• component of a chemical spray. when in contact with blood it emits a pale blue light.

• Most be performed in complete darkness.

• gives false positive on rust, paint and veggies.

What is a confirmatory blood test?

further testing that proves the presence of blood.

List examples of confirmatory tests for blood:

Takayama

Teichmann

Abacus HemaTrace Test Card

Which confirmatory test crystals look like this?

Teichmann

Which confirmatory test crystals look like this?

Takayama

What is the Abacus HemaTrace Test Card?

an immunochromatographic test, that replaces the use of crystal tests.

What does the Hema Trace test reacts to?

human hemoglobin

what are the steps of Hema Trace Test?

• hHB will react with the dye-conjugate.

• forming mobile antigen-antibody complex.

• complex migrates toward the test “T” region.

• “T” region captures the mobile complex.

• Becoming antibody-antigen-antibody sandwich.

• Pink color band form.

What is the lowest amount of hHB needs be present for a positive reaction on the ABAcard?

0.05 ug/mL in 10 minutes

What is Hook Effect?

when high amount of hHB is present and bind to antibody in test and the mobile antibody-Ag can’t bind

looking like a negative result.

How to overcome Hook Effect in ABAcards?

by diluting 1:100 and retesting

What are FTA cards?

FTA (Flinders Technology Associates)

• chemically treated paper used to collect, store, and transport biological samples.

• Usually sent by ME office.

What are the different sources of blood?

menstrual, child birth, fetal blood, normal shed blood.

What is porphyrin?

• derived from the cyclic ring compound porphin.

• has the ability to combine with metals.

Give an example of a porphyrin?

Hematin

It is the porphyrin ring combined with iron molecule.

What is the structural name of Heme?

Ferroprotophorphyrin

Ferro - (Fe2+)

Ferri - (Fe3+)

What are the 3 oxidation states of blood?

Heme → Oxyhemoglobin → Methemoglobin

I court do you provide opinion or comment on the age of blood?

No, I cant report or testify the age of any evidence.

My attempt is to answer the question of WHO, not the question of when, how or why.

Can phenolphthalin test all 3 states of oxidized blood?

Yes

How sensitive is phenolphthalin test?

the sensitivity is:

• 1:10^7 dilution for whole blood

• 1:10^6 dilution for decomposed blood