17) Analytical variables Flashcards
anything that may affect test results, which would result in an incorrect result
analytical variable
tracks errors and strives to find solutions to sources of error
quality assurance (QA) department
4 types of preanalytical variables
physiologic
specimen collection
handling of specimens
interferences
analytes affected by diurnal variation
BUN, aldosterone, bilirubin, catecholamines, cortisol, testosterone, luteinizing and follicle stimulating hormone, iron, potassium, thyroxine-stimulating hormone, triglycerides, uric acid and therapeutic drugs
analytes affected by exercise level
bilirubin, creatine kinase, aspartate aminotransferase, high-density lipoprotein cholesterol, lactate dehydrogenase, myoglobin, and uric acid
high protein diet effects
increase uric acid, urea, and ammonia levels
caffeine effects
decreases pH, increases ionized calcium and catecholamine levels
smoking effects
increases glucose, triglycerides, cholesterol, LDL cholesterol, ammonia
alcohol short term effects
decreases glucose, increase in plasma lactate, increases uric acid and triglycerides
alcohol moderate intake effects
increases HDL
alcohol long term effects
increases gamma glutamyltransferase, aspartate aminotransferase and alanine aminotransferase
prolonged fasting effects
Decreases prealbumin, glucose, albumin, LD, HDL cholesterol, ketones, and insulin
dehydration effects
Results in hemoconcentration, which falsely elevates iron, calcium, sodium, and enzymes
NIH recommendation for patient positioning
patients sit for 5 minutes before collecting a specimen for lipid testing
effects of standing vs supine
decrease in aldosterone, ADH, catecholamines, renin, albumin, ALP, ALT, bilirubin, calcium, cholesterol, total protein, and triglycerides
examples of physiologic variables
- age, ethnicity, gender
- diurnal variation
- exercise
- lifestyle/diet
- nonfasting/prolonged fasting
- dehydration
- pt position
examples of specimen collection variables
- requisition errors
- tourniquet time
- cleaning agent
- IV fluids/contamination
- drug interference
- capillary vs venous, serum vs plasma
- additives
- tube order
- short draw
- mixing
- labelling
- specific collections for micro
effects of long tourniquet time
increase in the ratio of cellular elements to plasma (hemoconcentration) and by causing hemolysis
analytes affected by long tourniquet time
those measuring large molecules, such as plasma proteins and lipids, or analytes affected by hemolysis, including potassium, lactic acid, and enzymes
betadine effects
falsely increase the phosphorus, uric acid and K+
Isopropyl (70%) alcohol cannot be used when…
collecting medical or legal ethanol specimens
IV draw procedure
not below IV
IV has been turned off for 2 – 5 min
draw a waste tube (10 mL, thrown away, usually a red top)
examples of IV contamination effects
Na and Cl may be increased, everything else diluted out.
Extremely high glucose, potassium, etc
analytes that require a conversion factor when EDTA plasma is used
cholesterol, triglycerides and HDL should be multiplied by 1.03 to be equivalent to a serum result
