Chemistry - Preanylitical Factors Flashcards
Use of isopropyl alcohol wipes to disinfect venipuncture site
Can compromise blood alcohol determination
Squeezing site of capillary puncture
↑ K+
Pumping fist during venipuncture
↑ K+, lactic acid, Ca2+, phosphorus; ↓ pH
Tourniquet >1 min
↑ K+, total protein, lactic acid
IV fluid contamination
↑ glucose, K+, Na+, Cl- (depending on IV). Possible dilution of other analytes.
Incorrect anticoagulant or contamination from incorrect order of draw
K2EDTA: ↓ Ca2+, Mg2+; ↑ K+ Sodium heparin: ↑ Na+ if tube not completely filled Lithium heparin: ↑ lithium Gels: Some interfere with trace metals & certain drugs
Hemolysis
↑ K+, Mg2+, phosphorus, LD, AST, iron, ammonia
Exposure to light
↓ bilirubin, carotene
Temperature between collection & testing
Chilling required for lactic acid, ammonia, blood gases
Inadequate centrifugation
Poor barrier formation in gel tubes can result in ↑ K+, LD, AST, iron, phosphorus
Recentrifugation of primary tubes
Hemolysis, ↑ K+
Delay in separating serum/plasma (unless gel tube is used)
↑ ammonia, lactic acid, K+, Mg2+, LD ; ↓ glucose (unless collected in fluoride)
Storage temperature
↓ at RT: glucose (unless collected in fluoride); ↑ at RT: lactic acid, ammonia; ↓ at 4ºC: LD ; ↑ at 4ºC: ALP
Diurnal variation
↑ in am: ACTH, cortisol, iron ↑ in pm: growth hormone, PTH, TSH
Day-to-day variation
≥ 20% for ALT, bili, CK, steroid hormones, triglycerides
Recent food ingestion
↑ glucose, insulin, gastrin, triglycerides, Na+, uric acid, iron, LD, Ca2+; ↓ chloride, phosphate, K+ Fasting required: fasting glucose, triglycerides, lipid panel
Alcohol
↓ glucose; ↑ triglycerides, GGT
Posture
↑ albumin, cholesterol, Ca2+ when standing
Activity
↑ in ambulatory patients: creatinine kinase (CK)
Exercise effects
↑ with exercise: K+, phosphate, lactic acid, creatinine, protein, CK, AST, LD
Stress
↑ ACTH, cortisol, catecholamines
