NPN Flashcards
Most abundant NPN in the blood
Urea
Take Note!
For urea analysis, avoid using sodium citrate and sodium fluoride additives for plasma
Urea conversion factor
0.357
BUN to urea conversion factor
2.14
Reference method for urea analysis
IDMS
Fearon Reaction produces what color by diacetyl monoxime?
Pink
Fearon Reaction produces blue color by?
Alkaline (hypochlorite or phenol)
Stage of Increased Concentration
Congestive Heart Failure
Shock, hemorrhage
Increased protein metabolism
High protein diet
Pre-Renal
Stage of Increased Concentration
Acute and chronic renal disease
Renal
Stage of Increased Concentration
Urinary Tract Obstruction
Post-renal
Decreased Concentration of Urea happens during
Low protein intake
Severe vomiting and diarrhea
Liver disease
Pregnancy
Urea to Creatinine Ratio
10:1 or 20:1
Increased urea, normal creatinine
Pre-Renal
Increased creatinine
Renal or Post-Renal
Decreased both
Post-Renal
Second most abundant NPN in the blood
Uric Acid
Take Note for Uric Acid!
Avoid icteric samples (peroxidases)
Do not use EDTA and sodium fluoride
anticoagulants/additives (inhibits uricase)
Use heparin for plasma samples (preferably red top)
Bilirubin and ascorbic acid destroys peroxidase enzyme
Conversion Factor for Uric Acid
0.0595
Uric acid + phosphotungstic acid – allantoin +
tungsten blue
Caraway Method
Decreased Concentration of Uric Acid occurs during
Liver disease
Defective tubular reabsorption (Fanconi)
Chemotherapy (azathioprine/6-mercaptopurine)
Overtreatment with allopurinol
Product of muscle contraction and energy (ATP) usage
Creatinine / Creatine
Amino Acid Components of Creatinine
Arginine
Glycine
Methionine
Conversion Factor of Creatinine
88.4
Take Note for Creatinine!
Ascorbic acid, glucose and alpha ketoacids may affect Jaffe reaction (creatinine)
Drug Interferences for Jaffe
Cephalosporin
Dopamine
Drug Interferences for Enzymatic
Lidocaine
Dopamine
Creatinine + Picric acid; Mixture of Reagent A and B – alkaline picrate; red-orange complex
(red tautomer)
Jaffe Method
Used to isolate creatinine from the sample
Fuller’s earth/Aluminum magnesium silicate
Lloyd’s reagent/sodium aluminum silicate
Creatininase-Hydrogen Peroxide
Creatinine is converted into creatine via?
Creatininase
Creatininase-Hydrogen Peroxide
Creatine is converted into sarcosine and urea via?
Creatine amidinohydrolase
Creatininase-Hydrogen Peroxide
Sarcosine is converted into glycine, formaldehyde and hydrogen peroxide via?
Sarcosine oxidase
Creatininase-Creatine Kinase
Creatine is converted into creatine phosphate and ADP via?
Creatine kinase
Creatininase-Creatine Kinase
ADP and Phosphoenolpyruvate is converted into pyruvate and ATP via?
Pyruvate kinase
Creatininase-Creatine Kinase
Pyruvate and NADH is converted into Lactate and NAD via?
Lactate Dehydrogenase
Product of protein metabolism → converted
immediately to urea by the liver
Ammonia
Take Note for Ammonia!
Used EDTA or Heparin anticoagulants
Extracted specimen should be placed on ice container immediately
Plasma for ammonia analysis is stable at -20oC for several days
Ammonia MOA: Microdiffusion chamber; Blood gas determination
Conway
Ammonia MOA: Glutamate dehydrogenase (urease method) – decreasing absorbance (NADH to NAD)
Enzymatic Method
Ammonia MOA: Bromphenol blue (intense blue in alkaline environment of ammonia)
Dry Slide Method
Creatinine is endogenous, synthesized by the body at constant rate (muscle mass), and majority is cleared by renal filtration; It is the relationship between urine and serum
creatinine
Creatinine Clearance
Low molecular weight protein produced by all tissues; Filtered and metabolized by the proximal convoluted tubules at fixed rate
Cystatin C
Assess renal transplant rejection; Also increased in myeloproliferative and
lymphoproliferative disorders
Beta-2-Microglobulin
May causes acute renal failure in patients with rhabdomyolysis
Myoglobin
Presence of protein in the urine
Urinalysis and Microalbuminuria
Protein produced by neutrophils and epithelial cells; Early marker of acute kidney injury; Upregulation of genes in renal ischemia, tubule injury and nephrotoxicity
Neutrophil Gelatinase-Associated Lipocalin
(NGAL)
Take Note for Cystatin C
Cystatin C – high within-subject variation (early
detection)
Creatinine – high between subject variation (for monitoring purposes)
Measured by urine or blood; Secretory ability – kidney must excrete since it is foreign substance
Phensulfonthalein Test
Concentrating ability of renal tubules; First morning – high SG, high concentration; Low SG, low concentration
Urine Specific Gravity
