4/10

• eGFR - Doesn’t use urine, In 2021, revision made to the equation because of further study: Serum creatinine x constant for gender
• other clearance tests: cystatin C and B-2 macroglobulin
• • Cystatin C
  • Completely cleared by glomerulus
  • Reabsorbed in metabolized form
  • Elevation of cystatin shown earlier than creatinine
  • Not normally in body
• • B-2 macroglobulin - Cleared by kidney but completely reabsorbed, thus better indicator of tubular function not glomerular (filtration function)
• the creatinase-H2O2 is used in the dry slide method
• creatinine analysis specimen uses plasma, serum, or urine
• creatinine analysis - the urine will be a 24 hour urine
• creatinine analysis - serum

  • fasting is not required
• if not analyzed immediately, urine should be refrigerated and frozen after 4 days
• interferences for creatinine analysis include hemolysis, icterus, sometimes lipemia or creatine (when diluted, get normal result)
• interferences of the Jaffe method include ascorbate, glucose, a-keto acids, uric acid – use kinetic measurement instead
• other interferences for creatinine analysis include cephalosporins, dopamine, lidocaine
• purines are two nitrogenous bases found in DNA
• uric acid is transported to the kidney via the bloodstream
• uric acid is filtered out by the glomerulus; upt o 98% reabsorbed by the proximal tubule; up to 70% is secreted into the distal tubules; the remainder is secreted into the GI tract
• ammonia is consumed by parenchymal cells of liver in production of urea
• high concentrations of ammonia are toxic as they are small ions that can cross the blood brain barrier
• As concentrations of ammonia get higher, causes personality changes, eventually coma, and then death
• • Plasma concentration of ammonia is not dependent on renal function (can produce alot of ammonia, if liver function is normal, will not have high concentration of ammonia in plasma)
• high amounts of urea indicate dysfunctional kidneys
• high levels of ammonia correlate with severe liver disease most commonly, as the liver is unable to make urea
• for ammonia assay, patient should not smoke for several hours before test
• children under 2 years old will have naturally higher ammonia levels