Term
| What is in the HBV vaccine? |
|
Definition
|
|
Term
| What is the serology of a patient who has had the hep B vaccine? |
|
Definition
| anti-HBsAg antibodies are positive (Anti-HBcAg= negative) |
|
|
Term
| HDV requires coinfection with ____ becaue it is _____. |
|
Definition
| hepatitis B, replication defective |
|
|
Term
| What HDV test are commercially available? |
|
Definition
| total anti-HDV antibodies |
|
|
Term
| What is the course of disease with hepatitis D coinfection with hepatitis B? |
|
Definition
| anti-HDV together with markers of acute HBV infection; low risk of chronicity |
|
|
Term
| What is the course of disease with super-infection with hepatitis B? |
|
Definition
| anti-HDV together with markers of chronic HBV infection; high risk of chronicity |
|
|
Term
| How can you tell whether a patient has recovered from their hep D? |
|
Definition
| anti-HDV antibodies disappear with recovery; anti-HDV antibodies remain positive with chronic infection |
|
|
Term
| What is another way to test for hepatitis D other than serology? |
|
Definition
|
|
Term
| Why is hepatitis C so likely to become chronic? |
|
Definition
| the virus mutates frequently |
|
|
Term
| T/F It is difficult to differentiate acute from chronic HCV infection. |
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Definition
|
|
Term
| Why is it difficult to distinguish acute versus chronic hep C infection? |
|
Definition
| IgM anti-HCV is frequently present in chronic infections; most accutely infected individuals (8 out of 10) remain asymptomatic |
|
|
Term
| How do you measure total anti-HCV antibodies (EIA)? |
|
Definition
| measured by enzyme-linked immunoassay (EIA) |
|
|
Term
| How long does it take for anti-HCV antibodies to become positive? |
|
Definition
| 6-8 weeks (do not identify early infections) |
|
|
Term
| In what situation would anti-HCV antibodies be falsely negative? |
|
Definition
|
|
Term
| What happens to anti-HCV antibodies overcourse of disease/with recovery? |
|
Definition
| nothing; they persist positive for life and do not distinguish between acute, chronic, or past infections |
|
|
Term
| What is the positive predictive value for total anti-HCV antibodies? |
|
Definition
| in high risk populations=99%; in low risk populations= 25% |
|
|
Term
| How do you confirm a positive anti-HCV (EIA)? |
|
Definition
| RIBA= recombinant immunoblot assay; measures antibodies against four recombinent HCV proteins, antibodies to two or more is positive; antibodies to one protein is indeterminant |
|
|
Term
| Which HCV RNA test is more sensitive? |
|
Definition
| the qualitative is more sensitive than the quantitative |
|
|
Term
| What is the quantitative HCV RNA test used for? |
|
Definition
| confirm the presence/absence of infection; predict response to therapy (>800,000 IU/mL associated with poor response), monitor response to therapy |
|
|
Term
| What is the qualitative HCV RNA test used for? |
|
Definition
| to confirm the presence/absence of infection |
|
|
Term
| Which confirmatory HCV test is more commonly used: quantitative or qualitative? |
|
Definition
| quantitative because in most infections HCV RNA is in the range of quantitative assays (however some prefer qualitative assay for confirmation as it is more sensitive and less expensive) |
|
|
Term
| What test is useful in patients with positive HCV antibodies and negative HCV RNA? |
|
Definition
|
|
Term
| What do positive HCV antibodies with negative HCV RNA mean? |
|
Definition
| may indicate that HCV infection has resolved, may be due to a false positive anti-HCV antibody test, may be due to a false negative HCV RNA test (use RIBA to rule out a false-positive HCV antibody result; HCV RNA test may be repeated in 6 months to rule out a false-negative RNA test result) |
|
|
Term
| What might cause a false negative HCV antibody test/ |
|
Definition
| acute HCV infection, immunocompromised state |
|
|
Term
| How long after infection does it take for HCV RNA to be detectable? |
|
Definition
|
|
Term
| How do you determine the genotype of HCV infection? |
|
Definition
| determined by sequencing of regions of the genome or by hybridization of a PCR amplicon to nitrocellulose strips coated with genotype-specific probes |
|
|
Term
| What is the most common HCV genotype in the US? |
|
Definition
|
|
Term
| What is the response of the different HCV genotypes to treatment? |
|
Definition
| 2 and 3 are more responsive; 1 is less responsive |
|
|
Term
| What are the noninvasive tests for H pylori infection? |
|
Definition
| serum antibodies to helicobacter, H pylori stool antigen (HPSA), urea breath test |
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|
Term
| What is the downside to using serum antibodies to test for helicobacter infection? |
|
Definition
| serum antibodies remain positive after infection eradication; do not differentiate between current and past infections |
|
|
Term
| Describe how the HPSA test is performed. |
|
Definition
| A stool sample is transferred into a diluent vial and agitated, few diluent drops are transferred into a reading plate; H. pylori is detected by an antibody tagged with an enzyme that acts on a substrate eliciting a color change |
|
|
Term
| How does the urea breath test work? |
|
Definition
| urea labeled with a carbon isotope is given orally, helicobacter produces urease which hydrolyzes the urea producing isotope labeled CO2 which is measured in exhaled air |
|
|
Term
| What are the invasive tests used to dx helicobacterpylori? |
|
Definition
| rapid urease test, special stains on biopsy, cultures |
|
|
Term
| What is a rapid urease test? |
|
Definition
| biopsy placed in a fluid or gel containing urea; the urease produced by helicobacter hydrolyzes urea releasing ammonia and bicarbonate, a pH change occurs revealed by a color change |
|
|
Term
| What special stains are used to detect helicobacter pylori infection? |
|
Definition
| warthin-starry (steiner), giemsa, immunohistochemistry |
|
|
Term
| Why would you want to culture someone's helicobacter pylori infection? |
|
Definition
| in order to test for sensitivity to antibiotics |
|
|
Term
| Which cells produce gastrin? |
|
Definition
| G cells of the gastric antrum |
|
|
Term
| Why might you order a test for serum gastrin levels? |
|
Definition
| to diagnose either Zollinger-Ellison syndrome or autoimmune gastritis |
|
|
Term
| What is zollinger-ellison syndrome? |
|
Definition
| gastrin-secreting tumor, most commonly located in the pancreas |
|
|
Term
| What parameters can be used to diagnose zollinger ellison syndrome? |
|
Definition
| fasting serum gastrin more than 10x the upper limit of normal, gastric pH less than or equal to 2, for equivocal cases the secretin test is used |
|
|
Term
| What is the secretin test? |
|
Definition
| when secretin is given intravenously and serial determinations of serum gastrin are measured; if serum gastrin does not decline, ZES is likely (a paradoxical increase may occur) |
|
|
Term
| What tests can be used to diagnose autoimmune gastritis? |
|
Definition
| gastrin levels, serum B12/CBC/PBS, put pts serum on gastric mucosa for immunoflourescence, schilling test |
|
|
Term
| What is the schilling test? |
|
Definition
| give pt radioactive B12 po. If 24 hr urine has low radioactive B12, administer radioactive B12 + intrinsic factor. If 24 hour urine radioactive B12 is low, you have malabsorption, if normal you have autoimmune gastritis |
|
|
Term
| What are the main tests used to diagnose acute pancreatitis? |
|
Definition
| serum amylase, serum lipase, urine amylase, amylase/creatinine clearance ratio |
|
|
Term
| In general the diagnosis of acute pancreatitis relies on what lab findings? |
|
Definition
| at least 3x elevation of serum amylase or lipase |
|
|
Term
| What are the advantages/disadvantages to using serum amylase to diagnose pancreatitis? |
|
Definition
| quick and cheap; degree of elevation may not reflect the severity of acute pancreatitis, with fulminent pancreatitis levels may decline; extensive necrosis may cause enzyme exhaustion |
|
|
Term
| What is the time course of serum amylase rise during pancreatitis? |
|
Definition
| levels increase early (in 2-12 hours) then peak in about 48 hours; return to normal within 5 days |
|
|
Term
| Which organs are the major sources of amylase? |
|
Definition
| pancreas and salivary glands |
|
|
Term
| What percent of patients with acute pancreatitis have nearly normal serum amylase levels? |
|
Definition
|
|
Term
| What kinds of pancreatitis are likely to have near normal amylase levels? |
|
Definition
| alcohol induced, relapsing pancreatitis, pancreatitis due to hypertriglyceridemia because it suppresses amylase activity |
|
|
Term
| Besides pancreatitis, serum amylase also is elevated d/t |
|
Definition
| cholecystitis, perforated ulcer, intestinal obstruction or ischemia,instrumentation (ERCP), after passing a gall stone, renal failure due to decreased clearance |
|
|
Term
| How do you determine whether serum amylase levels are due to pancreatitis or something? |
|
Definition
| values more than 3 x the upper limit of normal are highly suggestive of acute pancreatitis |
|
|
Term
| What's the difference between measureing urinary amylase and serum amylase? |
|
Definition
| urine amylase remains elevated longer than serum amylase (7-10 days) |
|
|
Term
| How do you calculate the amylase to creatinine clerance ratio (ACCR)? |
|
Definition
| 100 x (urinary amylase x serum creatinine)/(serum amylase x urinary creatinine) |
|
|
Term
| What is the most specific test for acute pancreatitis? |
|
Definition
|
|
Term
| What is the ACCR in acute pancreatitis? |
|
Definition
|
|
Term
| What kind of urine sample is needed for a ACCR? |
|
Definition
|
|
Term
| What kind of disease process interferes with the results of a ACCR? |
|
Definition
|
|
Term
| What test is used to diagnose macroamylasemia? |
|
Definition
|
|
Term
|
Definition
| in some individuals amylase attaches to IgA or IgG which is too large to be excreted in the urine; persistent hyperamylassemia but no clinical consequences; Characteristically they show elevated serum amylase and decreased urinary amylase (low amylase clearance) |
|
|
Term
| What is the time frame of serum lipase elevation during acute pancreatitis? |
|
Definition
| levels increase 4-8 hours after onset, may peak earlier than amylase (24 hrs), remain elevated longer (7-14 days) |
|
|
Term
| How does the sensitivity of serum lipase vs. amylase compare? |
|
Definition
| serume lipase may be less sensitive than amylase (more acute pancreatitis patients fail to show lipase elevation) |
|
|
Term
| What are the advantages to measuring serum lipase over amylase? |
|
Definition
| elevated in alcohol induced acute pancreatitis, little lipase activity is found outside the pancreas, remains normal with macroamylasemia |
|
|
Term
| What are the disadvantages to measuring serum lipase to dx acute pancreatitis? |
|
Definition
| lipase may rise with some acute abdominal problems, other than acute pancreatitis, that elevate amylase; renal insufficiency may elevate lipase |
|
|
Term
| Besides increased amylase and lipase, what are other findings in acute pancreatitis? |
|
Definition
| hyperglycemia, hypocalcemia, hyperbilirubinemia, elevation of ALP, leukocytosis, electrolyte disturbances |
|
|
Term
| How do you test for chronic pancreatitis? |
|
Definition
| low pancreatic enzymes (lipase, trypsin) and bicarb in duodenal fluid after stimulation (secretion, CCK), low pancreatic enzymes (trypsinogen) in serum, low pancreatic enzymes (chymotrypsin, elastase) in stool, high fecal fat (>7 g/day) due to malabsorption, hyperglycemia, abnormal glucose tolerance test |
|
|
Term
| What liver disease can occur with cystic fibrosis? |
|
Definition
|
|
Term
| The sweat test is AKA the... |
|
Definition
| quantitative pilocarpine iontophoresis |
|
|
Term
| How is a chloride sweat test performed? |
|
Definition
| pilocarpine is carried into the skin with an electric current (iontophoresis), stimulates sweat gland secretion, sweat is collected, chloride concentration is measured, CF patients have high levels of chloride |
|
|
Term
| How many CFTR gene mutations are there? |
|
Definition
|
|
Term
| What is the ddx for secretory diarrhea? |
|
Definition
| small intestine pathogens, mostly viruses, also toxigenic bacteria or parasites, self limited |
|
|
Term
| What is the ddx for exudative diarrhea? |
|
Definition
| colonic pathogens, mostly bacteria (toxigenic or invasive), sometimes parasites |
|
|
Term
| What defines an exudative diarrhea? |
|
Definition
| fecal WBC (more than 10 WBC/10 high power fields) |
|
|
Term
| How do you test for WBC in feces? |
|
Definition
| tests for neutrophil products: calprotectin and lactoferrin |
|
|
Term
| What test is indicated for diarrhea if tehre is evidence of exudation or fever? |
|
Definition
| obtain stool culture for pathogenic bacteria |
|
|
Term
| What are the steps for evaluating chronic diarrhea? |
|
Definition
| rule out parasites, repeat bacterial cultures, rule out malabsorption, systemic diseae, functional causes, test fecal calprotectin and lactoferrin, endoscopy with mucosal biopsy |
|
|
Term
| How do you rule out a parasite infection in a patient with chronic diarrhea? |
|
Definition
| 3 stool samples over 3 days for ova, cysts, and paracytes |
|
|
Term
| What systemic diseases can cause chronic diarrhea? |
|
Definition
| hyperthyroidism, diabetes, AIDS, tumor syndromes, other |
|
|
Term
| What is the IBD serology pannel? |
|
Definition
| anti-saccharomyces cerebesiae antibody (ASCA) IgG and IgA, atypical perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA) |
|
|
Term
| What is the typical serology of Crohn's disease? |
|
Definition
| p-ANCA-/ASCA+, IgG or IgA |
|
|
Term
| What is the typical serology of ulcerative colitis? |
|
Definition
|
|
Term
| How do you evaluate fat malabsorption? |
|
Definition
| fecal fat excretion (qualitative= microscopic, presence of fat globules, quantitative= grams/day), serum beta-carotene levels (fat soluble precursor of vitamin A that is adequately present in most diets) |
|
|
Term
| What tests detect small intestine dysfunction? |
|
Definition
|
|
Term
| What is the D-xylose test? |
|
Definition
| D-xylose is normally absorbed in the jejunum and poorly metabolized and excreted in the urine; D-xylose is given orally to a fasting patient, over 20% should be excreted in the urine over a 5 horu period, an abnormal test indicates jejunal malabsorption |
|
|
Term
| A schilling test that does not correct with IF supplementation indicates... |
|
Definition
| terminal ileum dysfunction |
|
|
Term
| What causes lactose malabsorption? |
|
Definition
|
|
Term
| Where is lactase in the GI tract? |
|
Definition
| brush border of small intestine |
|
|
Term
| What is the function of lactase? |
|
Definition
| breaks down lactose into glucose and galactose which are then absorbed |
|
|
Term
| What is the lactose tolerance test? |
|
Definition
| administer lactose and plasma glucose is unchanged, then administer glucose and plasma glucose rises |
|
|
Term
| What is the hydrogen breath test? |
|
Definition
| detects malabsorption of carbohydrates, an oral dose of carbohydrates such as lactose or fructose is given. If not absorbed, the carbohydrate is metabolized by colonic bacteria releasing hydrogen. The hydrogen is absorbed in the colon and exhaled in the breath. A peak of hydrogen measured in exhaled air indicates malabsorption |
|
|
Term
|
Definition
| a natural resin extracted from the guaiacum tree wood |
|
|
Term
| What is the MOA of the guaiac test/ |
|
Definition
| the heme in hemoglobin has peroxidase activity; when present in feces, heme catalyzes the oxidation of guaiac producing a color change. |
|
|
Term
| How many times should a guaiac test be administer before it is confirmed? |
|
Definition
| 3 consecutive stools should be sampled |
|
|
Term
| What can cause a false negative FOBT? |
|
Definition
| vitamin C which supresses the peroxidase activity |
|
|
Term
| What can cause a false positive FOBT? |
|
Definition
| peroxidase activity in meat, peroxidase activity in some vegetables (horseradish, artichokes, turnips, cauliflower, broccoli, others), NSAIDS can cause gastric mucosal bleeding |
|
|
Term
| To avoid having skewed results, what should you tell patients to do before doing a guaiac test? |
|
Definition
| avoid red meats, peroxidase rich vegetables, and excess vitamin C for 3 days and NSAIDS for 7 days |
|
|
Term
| What is the MOA of an immunochemical FOBT? |
|
Definition
| detects specifically human hemoglobin protein by an immunochemical reaction |
|
|
Term
| How many stool samples are needed for the immunochemical FOBT? |
|
Definition
|
|
Term
| Which is better immunochemical or guaiac FOBT? |
|
Definition
| immunochemical because it has superior specificity and does not require dietary restrictions; supreior sensitivity compared with guaiac test for colorectal lesions |
|
|
Term
| What are the downsides to immunochemical FOBT? |
|
Definition
| may detect only lower GI bleeding= hemoglobin from upper GI sources is generally degraded by digestive and bacterial enzymes and fails to react; more expensive and technically demanding than the guaiac test |
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