Serology

Blood and urine

Patient specimen most often tested

1 hr

Plain evacuated tube (serum) complete clot retraction

10 minutes

Centrifuged duration

Serum contaminated with erythrocytes

why is serum not recentrifuged

Heat

Coagulates protein

Bacterial growth

Alters protein (enzymes)

Lipemia

Interference

pH

Denature protein

Valid on some test

Icteric/Turbid serum suitability

• up to 72 hours → 2-8°C

• if more than 72h → Freeze

Specimen storage

• up to 72 hours → 2-8°C

• if more than 72h → Freeze

Complement Inactivation

Process that destroys complement

• Latex passive agglutination

• Hemagglutination

False positive causes in inactivated complement

• Heat 56°C for 30 min

• for 4 hours elapsed → 56°C for 10 mins (VDRL / RPR)

Physical complement inactivation

• Choline chloride

• thiomersal

Chemical complement inactivation

Within 2 hours of collection

Specimens should be tested promptly to produce accurate results

20°C

most volumetric glassware calibration temperature, and this is inscribed on the pipette

Graduated pipette

Used if great accuracy is not required

Smallest pipette

Pipette with greatest accuracy

Micropipettor

The most common type of micropipette used in many laboratories is one that is automatic or semiautomatic

Solute

Material being diluted: serum / sample

Diluent

The medium making up the rest of the solution

solute & diluent

The relationship between these two is expressed as a fraction

Implies 1 serum : 19 diluent

1:20 dilution ratio

Is the total volume (Solute + Diluent)

Bottom number of fraction

Dilution

Is an indication of relative concentration

Dilution factor

Used to correct for having used a diluted sample in a determination rather than the undiluted sample

Amount of Solute / Total Volume

1/Dilution

Compound Dilution

Dilution occurs in several stages

1:5 dilution of the original serum, a 1:10 dilution from the first dilution, and another 1:10 dilution (5 x 10 x 10 equals 500)

Ex. compound dilution: 1:500 dilution preparation method

Serial Dilution

If, in each step of the dilution, the dilution factor is exactly the SAME

Doubling dilution

Most common serial dilution, in which the amount of serum is cut in half with each dilution

• Acute phase of illness

• convalescent phase (2 weeks later)

Antibody Test blood draw timing

acute phase

when the disease is first discovered or suspected

Titer

Levels of antibody

Titer

Reciprocal of the highest dilution of the patient's serum in which the Ab is still detectable