- It is defined as all the complex steps required before sample analysis.
- The first and most crucial phase in the laboratory.
- It is the major source of residual error.
Pre-analytic phase
- Patient-related variables
- Specimen collection and labeling techniques
- Specimen preservatives and anticoagulants
- Specimen transport
- Specimen processing and storage
Pre-analytic factor
What are the most frequent pre-analytic errors?
- Improper filling of the sample tube
- Placing specimens in the wrong container or preservatives
- Selecting the incorrect test
What phase of the collection?
- Incorrect test ordered
- Inadequate patient preparation
- Misidentification of patient
Before collection
What phase of the collection?
- Wrong container & additive
- Short draw, wrong anticoagulant, and blood ratio
- Hemoconcentration from prolonged tourniquet time
- Hemolysis due to incorrect technique
During collection
What phase of the collection?
- Inadequate mixing or clots
- Mislabeling of specimen
- Improper transport to lab; exposure to light, extreme temperature, or delayed delivery
- Processing error; incomplete centrifugation, incorrect log-in, improper storage or aliquoting prior to analysis
After collection
Tests Affected by Diurnal Variation, Posture, and Stress
Peaks 4-6 AM; lowest 8 PM–12 AM; 50% lower at 8 PM than at 8 AM; increased with stress
Cortisol
Tests Affected by Diurnal Variation, Posture, and Stress
Lower at night; increased with stress
Adrenocorticotropic hormone (ACTH)
Tests Affected by Diurnal Variation, Posture, and Stress
Lower at night; higher standing than supine
Plasma renin activity (PRA)
Tests Affected by Diurnal Variation, Posture, and Stress
Lower at night
Aldosterone & Insulin
Tests Affected by Diurnal Variation, Posture, and Stress
Higher in afternoon and evening
Growth hormone & Acid phosphatase
Tests Affected by Diurnal Variation, Posture, and Stress
Increases with exercise
Thyroxine
Tests Affected by Diurnal Variation, Posture, and Stress
Higher with stress; higher levels at 4 and 8 AM and at 8 and 10 PM
Prolactin
Tests Affected by Diurnal Variation, Posture, and Stress
Peaks early to late morning; decreases up to 30% during the day
Iron
Tests Affected by Diurnal Variation, Posture, and Stress
4% decrease supine
Calcium
What physiologic factors exercise are given?
- Free fatty acid - Initial decrease then increase
- Lactase - It will increase 300%
- CK, AST, LD - It will increase
- Activates coagulation, fibrinolysis, and platelets
Transient effect
What physiologic factors exercise are given?
- CK, aldolase, AST, LD - It will increase
- Prolactin - elevated
- Serum gonadotrophin - decrease
Long-term effect
- It can greatly affect laboratory test results.
- The effect is transient and is easily controlled.
Diet
Physiological factor: Diet
- When determining blood constituents such as glucose, triglycerides, cholesterol, and electrolytes, collection should be done in the ___
Basal state
Physiological factor: Diet
- After how many hours of fasting when serum bilirubin increased?
48 hours
Physiological factor: Diet
- After how many hours of fasting when plasma glucose is decreased while plasma triglycerides, glycerol, and free fatty acids are increased.
72 hours
What would be the effect of mental and physical stress?
Increased ACTH, cortisol, and catecholamines
What would be the effect of mild stress?
Increased cholesterol and decreased HDL
What would be the effect of hyperventilation?
Acid-base balance is affected, elevated leukocyte count, serum lactate, and free fatty acid
