Flashcards in Enzymes of importance to Disease States Deck (44)
what is elevated in all forms of cholestasis and especially obstructive jaundice? In what other conditions may it be elevated?
alkaline phosphatase, ALP; in skeletal disease including Paget's, hyperparathyroid, fractures, bone tumors, and also during accelerated bone growth in kids
what would indicate a hepatocellular vs a cholestatic pattern on LFT analytes?
greater aminotransferase proportion to ALP, so increased AST or ALT
What conditions would cause ALT to predominate over AST if the condition is hepatocellular and not obstructive? What conditions are associated with more significant AST over ALT?
ALT is more specific for liver cell damage: acute or chronic hepatitis, steatohepatitis, cirrhosis,
AST is higher in 6 to 8 hours post AMI so is useful for ruling out concurrent liver damage, but it also is higher in musculoskeletal (like dystrophy) and pulmonary in which ALT is not as elevated
What enzyme would predominate in hepatocellular disease involving alcohol damage?
AST, aspartate transaminase
what analyte is most commonly used to evaluate kidney function?
BUN, blood urea nitrogen
what is azotemia?
elevation of nitrogenous productswith BUN usually elevated between 7 to 21 mg/dL, creatinine in blood and other waste products in blood
azotemia/ elevated BUN can be prerenal, renal, or postrenal. GIve some causes of prerenal
cardiac decompensation, increased dietary protein or increased protein catabolism, or dehydration, or loss of blood flow to kidney such as in lower blood volume, shock...
some causes of renal azotemia/elevated BUN
acute glomerulonephritis, chronic nephritis, polycystic kidney, nephrosclerosis, tubular necrosis
causes of post-renal azotemia?
obstructions such as kidney stones, enlarged prostate, tumors...
what ratio is often used instead of BUN for kidney function eval? what could cause a low ratio?
serum BUN to creatinine ratio; low protein intake, starvation, severe liver disease
Causes of high BUN to creatinine when creatinine normal?
catabolism of tissues, pre-renal azotemia, high protein intake
When in particular would AST be elevated? how many isoenzymes and which are elevated in what cases?
after an MI, or in hepatobiliary disease such as viral hepatitis, cirrhosis. The mitochondrial is only present in disease states; Cytoplasmic is found in normal serum
what is the more liver-specific enzyme and basic test principle?
Alanine aminotransferase, ALT. Like with AST, it is quatifies by using it on a substrate, then using the product of this (pyruvate here, but oxaloacetate for AST) to see a decrease in absorbance when NADH is oxidized
give approximate reference ranges for BUN and creatinine
BUN (urea): 8 to 24 mg/dL ( 7 to 20 another source; 2.5- 7 mmol/L)
Crea: 0.8 to 1.3mg/dL
how is creatinine clearance calculated (give formula) and what is an average range?
Urine crea/ serum crea x urine vol in ml/min for 24 hours x 1.73/ BSA
differs btw M/F and by age but generally 95 to 105 +/- 20 mL/min/1.73 m^2
what is the clin sig of incrsd or dcrsd uric acid? ref range?
increased in gout, renal disorders, lead poisoning, lactic acidosis (plus other)
decrsd in severe liver disease, tubular reabsorption disorders
F 2.6 -6, M 3.5 to 7.2 mg/dL.....think 3 to 7
what causes blood levels of ammonia to increase?
severe hepatocyte dysfunction, as they are supposed to convert it to urea bc ammonia is neurotoxic
how must a specimen for ammonia be handled?
on ice immed, collected in EDTA, centrifuge w/in 20 mins and remove plasma
what are lactate dehydrogenase isoenzymes differentiated by?
their constituent subunits, of combos of M (muscle/liver) polypeptides and H (heart) polypeptides
what are the groupings of LD isoenzymes associated with clinically (3 main groupings)
LD 1 and 2: AMI and RBC destruction---> bleeding hearts are #1!
LD3: pulmonary, pancreatitis, lymphocytosis
LD 4 and 5: liver and skeletal muscle---> dancing alcoholic
what isoenzyme of CK and what % of total CK is suggestive of AMI? what test will also be performed is suspected heart attack?
CK-MB at >6% ; a troponin assay
what is y-glutamyltransferase used to evaluate and how does it compare to other enzymes that may also elevate?
liver/bile duct disease (intra and post obstruction can cause levels 5 to 30X over ref range); bc it elevates first and stays high longer than ALT, AST and ALP: it is the more sensitive assay of hepatobiliary disease
does GGT elevate in bone disease? what does?
what test is highly specific for pancreatic disease and what is it often used in conjunction with? how quickly does it elevate, peak and stay elevated?
Lipase, often assayed with amylase; Lipase increases in 4 to 8 hours, peaks at 24, lasts 8 to 14 days (amylase rises faster and disappears in 3 days or so)
why would you test for G6PD ?
a deficiency (an X-linked genetic disorder) can cause drug-induced (or Fava bean!) hemolytic anemia, esp with antimalarial drugs; also infection can cause this anemia bc the enzyme is supposed to protect cells from oxidative damage by producing NADPH which donates electrons to glutathione to neutralize ROS, but there won't be enough for the increased demands of infection
What is troponin? what are the two types we measure and when do they elevate?
contraction-calcium-regulating proteins found in heart and skeletal muscle that rise in serum following damage; Troponin I of 1.0 ug + or Troponin T of 0.1 ug or higher is considered significant
what biomarker for MI is an early marker rising within 1 to 2 hours of symptom onset and effective for rule out within the 2 to 6 hour window after, but is not cardiac specific (can be higher in trauma, muscle injury, renal failure)...?
What are the 3 forms of natriuretic peptides? what are their functions?
ANP, BNP, and CNP
They promote excretion of sodium and water by increasing GFR and decreasing tubular reabsorption of sodium
What is the clinical significance and mechanism of BNP release/ function?
BNP is brain natriuretic peptide that is secreted by HEART ventricles when ventricles experience volume expansion and incrsd pressure; the BNP dilates vessels and promotes salt and water loss in order to reduce fluid load on the heart