Presentation on theme: "Laboratory Medicine Infectious Disease"— Presentation transcript:
1Laboratory Medicine Infectious Disease Brenda Beckett, PA-CClinical Assessment II
2Infectious Disease Urinalysis Serum serologies (antibody testing) Hepatitis, othersCultures: bacterial, viralRapid antigen testingO&PNosocomial infectionsCBC results with viral vs bacterial infection
3Specimen CollectionUrinalysis - clean catch used if culture is needed.Reflex testing - microscopic or culture if UA abnormalProper collection of cultures
4UrinalysisSpecimen type (clean catch, catheter, suprapubic aspiration, U-bag (nonsterile)Gross analysis - color, clarityDipstickMicroscopic - cellular elementsCulture if indicated: if infection is possible from dipstick or microscopic resultsReview sample UA
5Urinalysis Color: Normal = straw, light yellow. Amber/orange = bilirubin, urobilinogenRed = bloodOther colorsClarity: Normal = clearHazyCloudyArtifact or cellular elements
7Urine Dipstick Protein: Usually in form of albumin or globulins. Trace amounts in DM associated with increased mortality due to diabetic nephropathy.Globulins (Bence-Jones) associated with multiple myelomaLarge amounts in nephrotic syndrome
8Urine DipstickpH: Normal 5-9, usually around 6. Acidotic or alkalotic can be due to diet, medication, disease or metabolic changes. Some bacteria incr. pHSpecific Gravity: Normal Weight of particles in solution, correlates with osmolality.UTI increases pH
9Urine DipstickBilirubin: Increased in obstructive biliary disease, hepatocellular injury. Not incr in hemolytic jaundice.Urobilinogen: Formed by bacterial conversion of conj. Bilirubin in intestine. Incr in hepatocellular injury and jaundice, not obstructive biliary disease. Also increased in CHF with liver congestion, cirrhosis, hepatitis.
10Urine Dipstick Blood: Detects blood & hemoglobin. Can cross react with myoglobin.Increased in hemolysis, GU tract cancer, UTI, calculi, coagulopathies, glomerulonephritis.
11Urine DipstickGlucose: Present if serum glucose is > 180 mg/dL. Increased in DM.Ketones: Screening for ketoacidosis in diabetics. Increased in starvation, fever, pregnancy.
12Urine DipstickLeukocyte Esterase: Enzyme released by WBCs. Marker of infection or inflammationNitrite: Urine nitrates are converted to nitrite by some bacteria (E. coli, Klebsiella, Proteus, etc.)
13Microscopic Done if dipstick abnormal Detects cellular elements WBC RBCBacteriaEpithelial cells – if contaminated sample, or tubules sloughingCasts, crystalsSpin urine down to cellular elements
14Urine culture Semi-quantitative >100,000 colonies/ml indicative of infection>10,000 colonies/ml in symptomatic,immunosuppressed or abx treated patientsLower numbers suprapubic (>150)
15Serology Testing serum to determine antibody levels. Used for many viruses and other infectious agentsIgM - early infectionIgG - lifelong, immunity
16Hepatitis - CausesDrugs: antihypertensives, statins, antibiotics, others.Toxic agents: acetaminophen, alcohol, others.Viruses: Hepatitis A (HAV), B (HBV), C (HCV) commonly. Uncommon: EBV, CMV, measles, rubella, etc.
17Liver Function Tests Serum Aminotransferases (ALT and AST) Serum and urine BilirubinSerum Alkaline PhosphataseAdditionally: LDH, GGTP, Albumin, Prothrombin Time
18Liver Function Tests ALT – Alanine Aminotransferase AST – Aspartate AminotransferaseInflammation and cell necrosisMost sensitive marker of liver injury (from infections, toxins, autoimmunity, etc)
19Bilirubin Hemoglobin breakdown product Conjugated by liver, excreted in bile, eliminated in urineBilirubin increased in:Biliary tract obstruction (tumor, stone, pancreatitis)Inflammation (hepatitis)Hemolysis (Gilbert’s syndrome)
20BilirubinBilirubinuria occurs in both inflammation and obstruction (but not hemolysis)Jaundice results when levels exceed 2.5 mg/dlIn viral hepatitis, bilirubin not always elevated, therefore:Elevated serum bilirubin is neither sensitive nor specific for viral hepatitis
21More Liver Function Tests Serum albumin: decreased in cirrhosis and severe, fulminant diseaseProthrombin time: Prolonged in severe liver disease (vitamin K deficiency)LDH (lactate dehydrogenase): non specific, not very useful.ALKP: sensitive marker of biliary tract obstruction, mildly elevated in viral hep.
22Lab Findings ALT usually >8x upper limit of normal ALT usually elevated >ASTALKP modestly elevatedBilirubin normal to highly elevatedThese are quick tests if you suspect hepatitis.If elevated, proceed to serology testing
23Hepatitis A SerologyHAV IgM – rises early in illness, will remain positive for up to six months.HAV IgG – will appear soon after IgM and remain elevated for years.Most common cause of acute viral hepatitis (AVH), no chronicity, no carrier state
25Hepatitis A SerologyTesting for Hep A includes HAV Total (IgG and IgM), and HAV IgM. So,If someone has a positive HAV Total and an positive HAV IgM, they have a current infection.If someone has a positive Total and a negative IgM, they had a past infection or passive immunity (vaccination).
26Hepatitis B Second most common cause of acute viral hepatitis Most complex hepatitis virus -infective particle made up of viral core plus an outer surface coat5-10% become chronic, lead to cirrhosis, hepatocellular cancer
27Hepatitis B SerologyHBsAg: First evidence of infection, persists through clinical illness.Anti-HBs: Antibody to HBsAg appears after clearance of HBsAg and after vaccination (titer >=10 mU/mL).Neg HBsAg and pos Anti-HBs means recovery from HBV infection, noninfectivity and immunity.
28Hepatitis B Serology Anti-HBc: IgM anti-HBc appears shortly after HBsAg. Indicates acute hepatitis. Persists for 3-6 months or longer. May appear during flares of chronic HBV.IgG anti-HBc appears during acute HBV but persists indefinitely, whether recovery or chronic hepatitis occurs.
29Hepatitis B SerologyHBeAg: A soluble protein found in HBsAg positive patients. Indicates viral replication and infectivity. Appearance beyond 3 months indicates increased likelihood of chronicity.HBV DNA: Parallels presence of HBeAg, more sensitive and precise
32Hepatitis B ReviewAcute HBV: HBsAg+, IgM anti-HBc+, Total anti-HBc+, anti-HBs-, HBeAg+.Chronic HBV: HBsAg+, IgM anti-HBc-, Total anti-HBc+, anti-HBs-.Past resolved HBV: HBsAg-, IgM anti-HBc-, Total anti-HBc+, anti-HBs+.Vaccination (immunity): anti-HBs+.
33Hepatitis C Chronicity common (>70%) Prolonged viremia Aminotransferases elevated off and on (can have ALT >7x normal)Diagnose with Anti-HCV EIAFalse negatives early in disease (low sensitivity)False positives with elevated gamma glob (low specificity)
34Hepatitis C Serology Positive Anti-HCV EIA needs confirmation HCV RIBA (Recombinant Immunoblot Assay) confirms + EIA. Does not distinguish between past/present infection. Being replaced by HCV-RNALiver BiopsyHarder to dx just off of lab results
35Hepatitis C Serology HCV-RNA by RT-PCR. Most sensitive test Diagnose acute infection prior to seroconversionMay be intermittent (neg does not mean no disease)Qualitative and quantitative testsResponse to therapy
38Hepatitis C NO immunization No post exposure prophylaxis Chronicity commonDifferent genotypes respond differently to therapy
39Other Hepatitis Viruses Hepatitis D (Delta).Due to ssRNA virus.Always associated with Hepatitis B.Acute or chronic.Often severe, high mortality.Hepatitis E. Due to ssRNA virus.Rare, occurs in endemic areas.
40Chronic Hepatitis HBV – 5-10% of acute infections HCV - >70% of acute infectionsHDV – with HBV coinfection or superinfectionElevated aminotransferases for >6 monthsMy lead to cirrhosis, hepatocellular caLiver transplant may be indicated
43Review of Hepatitis Serology Excellent website with graphic representation of each type of viral hepatitis, case studies (click on “Training Resources”, then “Viral Hepatitis Online Serology Training”)
44HIV testing ELISA antibody (screening) Western Blot (confirmation) RNA PCR (viral load)CD4 count and %
45LYME AntibodiesLyme ab. IgM and IgG, screening with ELISA testing. Confirm with WBPoor sensitivity/specificityIgM – 2-4 wks post infection, decline by 4-6 monthsIgG – 4-8 wks post infection, high for months or yearsMust correlate clinically
46Antigen testing Tests for the actual infectious agent Example: Some Hepatitis testingRapid antigen tests: Rapid strep, Rapid flu, C. diff, etc. Test for a protein or other marker on the bacteria or virus, not a full culture
47Stool TestingO&P, will determine if there are parasites present in feces. May need more than one sample, not always shedding.Culture: tests for Salmonella, Shigella, Campylobacter, E.coli 0157WBC, occult blood (Guiac)C. diff - rapid antigen test
49Viral CulturesViruses are slow to grow in culture medium, may take weeks for a result.Therefore, serology is utilized more often.May see herpes culture ordered to confirm outbreak.
50Bacterial Cultures Sterile vs nonsterile site Normal flora Aerobic vs anaerobicGram stain is routinely performed on cultures from certain sites: sputum, wound, CSF, etc.Urine culture is semiquantiative others isolate bacterial colonies
51Common Specimens Eye – swab conjunctiva, corneal scrapings FB – IV cath tips, prosthetic heart valves, IUD, etc.GI – Gastric biopsy for H. pylori, rectal swab, stool for O&P, cultureGenital – cervical, urethral, vaginal secretions or swab.Resp – sputum, lavage, nasopharynx/pharynx swabTissue – biopsyUrine – clean catch, cath, suprapubic aspirateAbscess, pus, fluid – swab or aspirateBlood–special vacutainerBody fluids –(amniotic, pericardial, peritoneal, pleural, synovial) – needle aspirationCSF – lumbar punctureCutaneous-skin or nail scrapings, swab of infectionEar- middle ear myringotomy, outer ear swab
52Bacterial Culture – Gram stain Done quicklyOnly on certain sitesNeed to correlate with clinical pictureResults will be verified by culture in hrs, but can start empirically on antibioticsReport: Gram +/-, shape, other cellular elements (WBC, epithelials, etc)
58Bacterial Cultures Sensitivities if bacteria is a pathogen Antibiotics tested vary from lab to lab, depending on g+ or g-Certain species do not have sensitivities performed. Ex: Strep, usually sens to penicillins so no sensitivities performedHospital antibiogram – common bacteria and their susceptibilities
62Nosocomial Infections Originate in hospitalsAccount for tens of thousands of deaths per year5-10% of hospitalized patientsDue to:Prevalence of pathogensCompromised hostsEffective transmission
63Nosocomial Infections Primary pathogens:Enterococcus (VRE)E. coliPseudomonasStaph Aureus (MRSA)C. diffAcquire antibiotic resistanceBecome normal flora for hospital workersCommon sites: urinary tract, wounds, respiratory, skin, blood, GI
64CA MRSA Community acquired MRSA Athletes, children, military recruits, close living quartersNot hospitalized or in long-term care
65WBC overview Viral vs. bacterial infection Sepsis Viral: lymphocyte response (T, B or NK). May have slightly elevated or suppressed total WBC countBacterial: Neutrophil response with early forms (bands). Often higher total WBCSepsisNeutropenia or neutrophilia, immature forms