Introduction to Clinical Laboratory Testing Seminar Exam #2

Major types of specimens tested

blood, stool, urine, body fluids

General Procedure for a UA

• observe : color, clarity, odor

• Transparency (clarity)

• Odor

• Foam

• Use dip stick 

• Measure for specific gravity (total dissolved solids) using the dip stick -> normal : 1.002-1.040

• Perform confirmation tests when required

• Perform microscopic evaluations for cell types

Procedure for Microscopic Evaluation of Urine

1. Pour aliquot into centrifuge tube

2. Pour off supernate, resuspend pellet, put drop on slide and coverslip

3. Observe on low power for casts high power for cells, crystals, bacteria

What you're looking for during micro eval:

• RBC’s

• WBC’s

• Epithelial cells: squamous, transitional, renal tubular

Body Fluids:

• CSF

• Seminal fluid

• Amniotic fluid: tests for neural tube defects and the AFP (alpha-feto protein) and assess fetal lung maturity (lecithin/sphingomyelin ratio) ->should be 2:1 or >, otherwise respiratory distress

• Synovial Fluid

• Serous fluids

• semen

blood specimens

• Arterial- blood gas

• Venous- routine lab test

• Whole blood

• Plasma: received via centrifuge 

blood procedure

Blood collected and then centrifuged 

Organizational structure of clincical pathology department

(a) Chemistry/Urinalysis

(b) Microbiology

(c) Hematology and Coagulation

(d) Immunology

(e) Blood Bank

(f) Molecular Diagnostics

organizational structure for anatomic pathology

(a) Histology

(b) Cytology

(c) Autopsy/Morgue

(d) Surgical Pathology

When and Why does the testing get done?

1. Presence or absence of disease

2. Monitor treatment

3. Preventative

4. Evaluate nutritional status

5. Toxicology and Therapeutic Drug Monitoring

6. Determine cause of death

Quality Assurance (QA)

Overall program to ensure reliable results. Technical and non-technical components.

Components of QA

• Patient test management

• Procedure manual

• QC assessment

• Proficiency testing – facility match to nation results

• Comparison of results – between machine and micro

• Communications – shift to shift 

• Complaint investigations

• Records – errors, QC 

• QA review with staff

• Personnel Assessment – performance review 

Quality Controls (QC)

– Daily checks for accuracy and precision

Components of QC

1. Reliability: Accuracy and Precision

accuracy – how close a test is to its true value (controls precision – reproducibility of results

2. Variance – fluctuation

3. Level of complexity – dictates type and frequency of controls

4. Controls – known-value samples run like patient specimens

5. Preventative maintenance (PM) – yearly checkup for instruments

True positive

sick people correctly diagnosed with disease.

false positive

• healthy people incorrectly identified as sick.

true negative

healthy people correctly labeled free of disease.

false negative

Sick people incorrectly identified as healthy.

sensitivity

• the likelihood that a test will be positive in the presence of a particular disease.

• True positives in diseased patients

specificity

• the likelihood that a test will be negative in the absence of a particular disease.

• True negatives in healthy patients

Normal/Reference ranges:

• healthy averages (without disease) from hospital to hospital (it can change/there is variability)

How the normal reference ranges are obtained:

•  statistically using a bell curve and getting the mean +/- 2SD from the bell curve

Functional unit of kidney:

nephron -> Glomerulus filters blood; tubules adjust composition

Basic urine composition:

• 96% water

• 4% dissolved substances (urea, creatinine)

polyuria

• increased urine output

• diabetes, neurotic states, tumors of CNS

 Oliguria

• decreased urine output in a 24hr period

• Renal – ischemia, drugs, glomerulonephritis

• Dehydration, obstruction, cardiac insufficiency

Anuria

• no urine output

• obstruction, acute cortical necrosis, acute tubular

• necrosis, hemolytic transfusion reaction