Clinical Lab Medicine I

What are the major specimen types tested in clincal labs?

Blood

Urine

Stool

Body fluids (CSF, synovial, amniotic, semen)

Difference between arterial vs. venous blood?

Arterial = blood gases

Venous = routine labs

Difference between plasma and serum?

Plasma = Containing clotting factors

Serum = No clotting factors (post-centrifugation)

What is a midstream clean catch used for?

Urine culture (reduce contamination)

What are the main divisions of pathology?

Clinical pathology

Anatomic pathology

What does clinical pathology include?

Chemistry

Hematology

Microbiology

Immunology

Blood bank

Molecular

What does anatomic pathology include?

Histology

Cytology

Autopsy

Surgical pathology

Who performs lab testing?

Pathologists

PAs

Scientists

Technologists

Technicians

Nurses and PAs

Who has the highest level of training in lab?

Pathologists (MD)

List key reasons for lab testing

Presence/Absence of disease

Monitor treatment

Preventative

Evaluate nutritional status

Toxicology and therapeutic drug monitoring

Determine cause of death

What is the difference between QA and QC?

QA = Overall program to ensure reliable results

QC = Daily check for accuracy and precision (quality control)

What are the 5 categories of QC?

Reliability

Variance

Level of complexity

Controls

Preventative maintenance (PM)

Define accuracy vs. precision

Accuracy = Closeness to true value

Precision = Reproducibility

What are controls?

Known samples run to verify test performance

What is proficiency testing?

Comparing lab results to national standards

Define sensitivity

The likelihood that a test will be positive in the of a particular disease

True positrive in diseased patients

Define specificity

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

True negative in healthy patients

Define true positive

Sick patient correctly identified

Define true negative

Healthy patient correctly identified free of disease

Define false positive

Healthy patient incorrectly labeled sick

Define false negative

Sick patient incorrectly labeled as healthy

Screening vs. Confirmatory tests?

Sensitive but not specific

More specific

How are rerefernce ranges established?

Mean ± 2 standard deviations (bell curve)

Why is variability normal?

Biological and measurement variation

Functional unit of the kidney

Nephron

Basic urine composition?

96% water

4% solutes

Why perform urinalysis?

Screening

Diagnosis

Monitoring disease/treatment

What is polyuria?

Increase urine output

What is oliguria?

Decreased urine output

What is anuria?

No urine output

What are types of UA specimens?

Random

First morning void'

Timed (24 hrs)

Mid stream clean catch for culture

Catheterized specimen

Suprapubic aspirate

Reasons for performing a UA

Inexpensive screening method

Readily available

Easy to collect

Diagnose disease

Monitor disease

Monitor treatment

What is the first step in UA?

Observe color, clarity, odor

Normal urine color?

Yellow

What does an ammoniacal odor indicate?

Urea broken down

What does fruit odor indicate?

Ketones

What would white, large amount of foam indicate in UA?

May be proteins

Normal specific gravity?

1.002-1.040

Glucose in urine indicates?

Diabetes (overflow after threshold exceeded)

Ketone indicates?

Fat breakdown

Protein in urine indicates?

Kidney damage (glomerular or tubular)

Nitrites indicate

Bacterial infection

Leukocyte esterase indicates?

WBCs → Infection

What is the normal pH?

5-8

What should be negative in urine?

Glucose

Ketones

Protein

Bilirubin

Blood

Nitrites

Leukocyte esterase

What is nephrotic syndrome?

Massive loss of protein

Generalized edema

Albuminemia

Lipiduria

Normal RBCs in urine?

0.2/hpf

Normal WBCs in urine?

0-5/hpf

Pyuria means?

Increased WBCs (infection)

What are casts made of?

Tamm-Horsfall proteins

RBC casts indicates?

Glomerulonephritis

WBC casts indicate?

Infection/Inflammation

Fatty casts indicate?

Severe renal disease

Crystal depend on what?

Urine pH

What produces acidic urine crystals (pH 6.5 or <)?

Uric acid

Calcium oxalate

What produces alkaline urine crystal (pH 7.0 or >)?

Phosphates

CSF function?

Cushion brain

Regulate pressure

Remove waste

What does gout look like microscopically?

Chalky white

How is CSF collected?

Lumbar puncture (L4-L5)

What does decreased CSF glucose indicate?

Bacterial meningitis

Increase neutrophils in CSF?

Bacterial infection

What are the three types of serous fluid?

Pleural

Pericardial

Peritoneal

Synovial fluid function?

Joint lubrication

Amniotic fluid used for?

Genetic testing

Fetal lung maturity

Semen analysis evaluates?

Fertility

Transudate characteristics?

Low protein, clear, low cells

Exudate characteristics?

High protein, cloudy, high WBC