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Point of Care Testing and Microbiology

Point of Care Testing and Microbiology. Yvette S. McCarter, PhD, DABMM Director, Clinical Microbiology Laboratory University of Florida Health Science Center-Jacksonville Jacksonville, FL Clinical Associate Professor of Pathology University of Florida College of Medicine.

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Point of Care Testing and Microbiology

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  1. Point of Care Testing and Microbiology Yvette S. McCarter, PhD, DABMM Director, Clinical Microbiology Laboratory University of Florida Health Science Center-Jacksonville Jacksonville, FL Clinical Associate Professor of Pathology University of Florida College of Medicine

  2. Point of Care Testing and Microbiology Objectives • Historical Perspective • POCT – Clinically-relevant? Cost-effective? • Currently available Microbiology POCT • Advantages and disadvantages of Microbiology POCT

  3. Point of Care Testing Historical Perspective Clinical Ward Laboratory Testing Centralized Laboratory Testing Point of Care Testing

  4. Centralized Lab Test ordered Test request processed Specimen obtained Specimen transported to lab Specimen processed by lab Specimen analyzed Results reviewed by lab staff Results reported to clinician Clinician acts on results Point of Care Test ordered Specimen obtained Specimen analyzed Clinician acts on result Test Life Cycle

  5. Why is Point of Care testing a clinically relevant alternative to centralized testing? Decreased Turnaround Time

  6. Why decreased turnaround time? Elimination of specimen transport and processing time

  7. Transport/Processing Time vs. Analysis Time Salem et al. JAMA 1991; 266:382-389

  8. Clinical Benefits of Decreased Turnaround Time • Evidence-based medical decisions in “real time” • Eliminates need for ordering additional, unnecessary tests • Reduction in unneeded medications • Decrease in physician “switching” • Perceived patient benefits

  9. Economic Considerations COST!!!! • Look beyond “cost per test” • Judge cost-effectiveness in the context of “total cost of patient care”

  10. Why is Point of Care testing a cost-effective alternative to centralized testing? Decreased Turnaround Time

  11. Economic Benefits of Decreased Turnaround Time • Reduction in duplicate test orders • Reduced consumption of other expensive services/products (lab tests, pharmaceuticals) • Decreased length of stay

  12. Economic Benefits of Decreased Turnaround Time Point of Care Testing in the Post Anesthesia Care Unit • Use of POCT resulted in: • reduced test TAT from 26 min to 2 min • decreased length of stay by 18 min • documented cost savings due to decreased length of stay Goodwin MLO 1994; 26 (9S):15-18.

  13. Microbiology Point of Care Testing

  14. “Your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.” -Dr. Ian Malcolm Jurassic Park

  15. Why do we need it? • Evidence-based medical decisions in “real time” • Eliminates need for ordering additional, unnecessary tests • Reduction in unneeded medications • “Perceived” patient benefits • Reduction in duplicate test orders • Reduced consumption of other expensive services/products (lab tests, pharmaceuticals)

  16. What to consider… • Choose the appropriate test • Difficulty? • Necessary skill level? • How much QC? • Training • See one, do one, teach one • Procedure • Don’t assume • Pictures

  17. Microbiology Point of Care Testing Most common • Group A streptococcal pharyngitis • Helicobacterpylori antibody • Helicobacterpylori • HIV antibody • Provider Performed Microscopy • Skin KOH • Vaginal KOH • Vaginal wet preps

  18. Microbiology Point of Care Testing Additional testing available • Influenza A, B and A/B • Infectious mononucleosis • Lyme antibody • Respiratory syncytial virus • Pinworm preps • Gram stain

  19. Group A Streptococcal Pharyngitis • Acute pharyngitis=most frequent reason for pediatrician and PCP visits • Most pharyngitis viral in origin • Group A strep  15% of pharyngitis cases in children • Difficult to distinguish streptococcal and non-streptococcal disease

  20. Group A Streptococcal Pharyngitis

  21. Group A Streptococcal Pharyngitis

  22. Group A Streptococcal Pharyngitis • Early recognition and treatment important • Shorten duration of clinical illness • Prevent transmission • Prevent sequelae • Rheumatic heart disease • Glomerulonephritis

  23. Group A Streptococcal Pharyngitis - Diagnosis • Culture • Gold standard • 24-48 hr result • Rapid antigen tests • Enzyme immunoassays (POCT) • Optical immunoassays • Nucleic acid based tests

  24. Group A Streptococcal Pharyngitis - POCT Pediatric Setting • Evaluated 2401 patients with suspected streptococcal pharyngitis with rapid latex test and culture • Conclusions • Rapid test available while patient on-site • Same day Rx in 90% of patients Wiedermann et al. J Am Board Fam Pract 1991; 4:79-82

  25. Group A Streptococcal Pharyngitis - POCT Emergency Department • Compared clinical judgment vs. rapid testing for diagnosis of pharyngitis in 147 patients • Conclusions • Rapid test significantly better than clinical judgment for determining disease • Rapid test eliminates problems/costs of empiric Rx and patient follow-up compliance • Only 14% of patients followed up on cultures DuBois et al. Ann Emerg Med 1986; 15:157-159

  26. Group A Streptococcal Pharyngitis - POCT Primary Care Setting • Studied impact of rapid test on physician prescribing patterns • Conclusions • Antibiotic prescribing patterns changed when rapid test used • Physicians initiated Rx with positive result and waited for culture before initiating Rx with negative result • Reduced inappropriate antibiotic usage • Reduced unnecessary cost and antibiotic exposure True et al. J Fam Prac 1986; 23:215-219

  27. 37 CLIA “waived” tests Abbott Signify Biostar Acceava Binax NOW Quidel QuickVue BD LINK Meridian ImmunoCard Group A Streptococcal Pharyngitis - POCT

  28. Advantages Results in 5 min Internal controls Clear endpoints Disadvantages Sensitivities lower than company claims Group A Streptococcal Pharyngitis - POCT

  29. Group A Streptococcal Pharyngitis - POCT • Things to remember… • Verification of test against culture • Culture all negative tests • Rapid test collection swab often different from culture swab

  30. Helicobacter pylori Infection • Early 1980s link between H. pylori and peptic ulcer disease/gastric cancer established • Epidemiology • Up to 50% of world’s population infected • Fecal-oral and oral-oral spread • Prevalence of infection increases with age (developed countries)

  31. Helicobacter pylori Infection • Pathology • Lives under protective mucous layer • Acute gastritis chronic active gastritis • Duodenal ulcer • MALT lymphoma • Gastric ulcer • Gastric carcinoma

  32. Helicobacter pylori Infection

  33. Helicobacter pylori Diagnostic Methods • Noninvasive • Antibody detection • IgG (POCT) • IgA • Urea breath test • Stool antigen

  34. Helicobacter pylori Diagnostic Methods • Invasive • Biopsy (multiple required) • Histopathology • Silver or Warthin-Starry stains • Rapid urease testing (POCT) • Agar based gel or paper strip • Culture

  35. Helicobacter pylori POCT • Biopsy • 7 CLIA “waived” tests • Serim PyloriTek • CLOtest • Chek-Med Systems HP One • Serology • 18 CLIA “waived” tests • Meridian ImmunoCard STAT • Abbott Signify • Quidel QuickVue

  36. Helicobacter pylori POCT

  37. Helicobacter pylori POCT

  38. Advantages Rapid results 15 min-24 hr Internal controls Room temperature storage and incubation Disadvantages Potential for false negatives Helicobacter pylori POCT Rapid Urease Testing

  39. Advantages Rapid results 5 min Built in controls External controls Room temperature storage Disadvantages Whole blood less sensitive than serum Helicobacter pylori POCT Antibody Detection

  40. HIV Infection The Virus • Retrovirus • Bar-shaped core • 2 short strands of RNA • Enzymes • Reverse transcriptase • Protease • Ribonuclease • Integrase • Outer lipid envelope containing an antigen (gp160) that helps virus bind to CD4 cells

  41. Adult prevalence rate 15.0% – 36.0% 5.0% – 15.0% 1.0% – 5.0% 0.5% – 1.0% 0.1% – 0.5% 0.0% – 0.1% not available A global view of HIV infection33 million adults living with HIV/AIDS as of end 1999

  42. Diagnosis of HIV • Culture • Rarely performed • Serology - Gold Standard • Sensitive EIA • Confirmatory Western blot • Window period • P24 antigen • PCR

  43. Diagnosis of HIV • Alternative Fluids and Home Collection • OraSure • Oral mucosal transudate - serum derived fluid, enters saliva from gingival crevices, contains antibody • Can be used for EIA and Western blot testing, comparable sensitivity to serum • Calypte (Sentinel) • Urine • Lower sensitivity and specificity than serum for diagnosis • No FDA licensed Western blot • Home Access • Finger stick, mail in blood spot for testing • Pre and post test counseling • Problem with improperly collected specimens

  44. 1 CLIA “waived” test OraQuick Rapid HIV-1 Antibody Test Diagnosis of HIV - POCT

  45. Diagnosis of HIV - POCT Public Health Setting • Evaluated 1923 samples from STD clinics and HIV counseling centers using SUDS and conventional EIA / WB • Conclusions • SUDS sensitivity 100%, PPV 88% (STD), PPV 81% (HIV) • Rapid testing feasible in public health settings (accurate, reasonable cost, results during visit) Kassler et al. J Clin Microbiol 1995: 33:2899-2902

  46. Diagnosis of HIV - POCT • Labor and Delivery • Evaluated 380 women presenting with unknown HIV status • Compared OraQuick performed in L&D and lab • Conclusions • Median TAT POCT=45 min, lab=3.5 hr • More rapid implementation of antiviral Rx with POCT MMWR 2003; 52:866-868

  47. Diagnosis of HIV - POCT • Appropriate settings • Evaluation of needlestick exposures • Labor and Delivery • Previously untested for HIV • Public Health • STD clinics • HIV counseling centers • ED

  48. Advantages Rapid results Counseling Rx Internal controls Accurate Disadvantages Must confirm positive results “Restrictions” Diagnosis of HIV - POCT

  49. Diagnosis of HIV - POCT Restrictions • Sale restricted to clinical laboratories • that have an adequate QA program; and • where there is assurance operators will receive and use instructional materials • Approved only for use by an agent of a clinical laboratory • Test subjects must receive “Subject Information” prior to collection and appropriate information when results are provided • Not approved to screen blood or tissue donors

  50. Diagnosis of HIV - POCT • Things to think about… • Can a central lab give you adequate TAT? • Who will be doing the testing? • What about positives? • PT • RHIVW (CAP)

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