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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 Point of Care Testing and Microbiology Objectives Historical Perspective POCT – Clinically-relevant? Costeffective? Currently available Microbiology POCT Advantages and disadvantages of Microbiology POCT Point of Care Testing Historical Perspective Clinical Ward Laboratory Testing Centralized Laboratory Testing Point of Care Testing Test Life Cycle 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 Why is Point of Care testing a clinically relevant alternative to centralized testing? Decreased Turnaround Time Why decreased turnaround time? Elimination of specimen transport and processing time Transport/Processing Time vs. Analysis Time 40 35 TAT (min) 30 25 Analysis Time 20 Transport/Processing Time 15 10 5 0 Blood Gases K+/Na+ Hematocrit Salem et al. JAMA 1991; 266:382-389 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 Economic Considerations COST!!!! Look beyond “cost per test” Judge cost-effectiveness in the context of “total cost of patient care” Why is Point of Care testing a costeffective alternative to centralized testing? Decreased Turnaround Time 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 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. Microbiology Point of Care Testing “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 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) 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 Microbiology Point of Care Testing Most common Group A streptococcal pharyngitis Helicobacter pylori antibody Helicobacter pylori HIV antibody Provider Performed Microscopy Skin KOH Vaginal KOH Vaginal wet preps 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 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 Group A Streptococcal Pharyngitis Group A Streptococcal Pharyngitis Group A Streptococcal Pharyngitis Early recognition and treatment important Shorten duration of clinical illness Prevent transmission Prevent sequelae Rheumatic heart disease Glomerulonephritis Group A Streptococcal Pharyngitis - Diagnosis Culture Gold standard 24-48 hr result Rapid antigen tests Enzyme immunoassays (POCT) Optical immunoassays Nucleic acid based tests 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 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 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 Group A Streptococcal Pharyngitis - POCT 37 CLIA “waived” tests Abbott Signify Biostar Acceava Binax NOW Quidel QuickVue BD LINK Meridian ImmunoCard Group A Streptococcal Pharyngitis - POCT Advantages Results in 5 min Internal controls Clear endpoints Disadvantages Sensitivities lower than company claims 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 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) Helicobacter pylori Infection Pathology Lives under protective mucous layer Acute gastritis chronic active gastritis Duodenal ulcer MALT lymphoma Gastric ulcer Gastric carcinoma Helicobacter pylori Infection Helicobacter pylori Diagnostic Methods Noninvasive Antibody detection IgG (POCT) IgA Urea breath test Stool antigen 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 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 Helicobacter pylori POCT Helicobacter pylori POCT Helicobacter pylori POCT Rapid Urease Testing Advantages Rapid results 15 min-24 hr Internal controls Room temperature storage and incubation Disadvantages Potential for false negatives Helicobacter pylori POCT Antibody Detection Advantages Rapid results 5 min Built in controls External controls Room temperature storage Disadvantages Whole blood less sensitive than serum 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 A global view of HIV infection 33 million adults living with HIV/AIDS as of end 1999 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 Diagnosis of HIV Culture Rarely performed Serology - Gold Standard Sensitive EIA Confirmatory Western blot Window period P24 antigen PCR 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 Diagnosis of HIV - POCT 1 CLIA “waived” test OraQuick Rapid HIV-1 Antibody Test 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 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 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 Diagnosis of HIV - POCT Advantages Rapid results Counseling Rx Internal controls Accurate Disadvantages Must confirm positive results “Restrictions” 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 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) Provider Performed Microscopy Things to think about… Training and continued proficiency Pictures Use of “live” specimens Microscope Conclusions Decide first if test needs to be done at point of care Pick the right test Keep in mind the manual nature of the testing
