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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
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Point of Care Testing and Microbiology
Objectives Historical Perspective POCT – Clinically-relevant? Cost-effective? Currently available Microbiology POCT Advantages and disadvantages of Microbiology POCT
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Historical Perspective
Point of Care Testing Historical Perspective Clinical Ward Laboratory Testing Centralized Laboratory Testing Point of Care Testing
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Test Life Cycle Centralized Lab Point of Care 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
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Decreased Turnaround Time
Why is Point of Care testing a clinically relevant alternative to centralized testing? Decreased Turnaround Time
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Elimination of specimen transport and processing time
Why decreased turnaround time? Elimination of specimen transport and processing time
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Transport/Processing Time vs. Analysis Time
Salem et al. JAMA 1991; 266:
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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
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Economic Considerations
COST!!!! Look beyond “cost per test” Judge cost-effectiveness in the context of “total cost of patient care”
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Decreased Turnaround Time
Why is Point of Care testing a cost-effective alternative to centralized testing? Decreased Turnaround Time
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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
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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.
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Microbiology Point of Care Testing
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“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
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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)
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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
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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
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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
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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 More common in children and young adults Most MDs overcall strep throat based solely on clinical grounds Clinical=sore throat, red, white patches on back of throat/tonsils, swollen lymph nodes, fever, headache
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Group A Streptococcal Pharyngitis
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Group A Streptococcal Pharyngitis
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Group A Streptococcal Pharyngitis
Early recognition and treatment important Shorten duration of clinical illness Prevent transmission Prevent sequelae Rheumatic heart disease Glomerulonephritis
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Group A Streptococcal Pharyngitis - Diagnosis
Culture Gold standard 24-48 hr result Rapid antigen tests Enzyme immunoassays (POCT) Optical immunoassays Nucleic acid based tests
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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
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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 PPV rapid = 78% PPV clinical = 38% Also did culture DuBois et al. Ann Emerg Med 1986; 15:
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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:
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Group A Streptococcal Pharyngitis - POCT
37 CLIA “waived” tests Abbott Signify Biostar Acceava Binax NOW Quidel QuickVue BD LINK Meridian ImmunoCard
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Group A Streptococcal Pharyngitis - POCT
Advantages Results in 5 min Internal controls Clear endpoints Disadvantages Sensitivities lower than company claims
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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
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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) Developed countries – infection in childhood (WWII) in developing countries prevalence not related to age
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Helicobacter pylori Infection
Pathology Lives under protective mucous layer Acute gastritis chronic active gastritis Duodenal ulcer MALT lymphoma Gastric ulcer Gastric carcinoma Under mucous layer pH=neutral. HP splits urea to form ammonia Urease = important survival mechanism
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Helicobacter pylori Infection
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Helicobacter pylori Diagnostic Methods
Noninvasive Antibody detection IgG (POCT) IgA Urea breath test Stool antigen Most patients produce measurable immune response IgG tests have markedly decreased sensitivity in HIV + patients Antibody good for diagnosis of uncomplicated cases Whole blood POCT assays have reduced sensitivity 80-90% compared to serum EIAs Urea breath test Drink isotopically labeled urea in water, breath collection min later, measure labeled CO2. More useful for evaluation of patients with symptoms after treatment (cost)
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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 Organisms almost never visualized within ulcer Biopsies usually taken from antrum and corpus
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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
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Helicobacter pylori POCT
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Helicobacter pylori POCT
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Helicobacter pylori POCT
Advantages Rapid results 15 min-24 hr Internal controls Room temperature storage and incubation Disadvantages Potential for false negatives Rapid Urease Testing
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Helicobacter pylori POCT
Advantages Rapid results 5 min Built in controls External controls Room temperature storage Disadvantages Whole blood less sensitive than serum Antibody Detection Antibody Indirect indicator of active infection Only test patients with GI symptoms Asymptomatic individuals with H. pylori Increase in “colonization” in older age groups May persist for years in treated patients-cannot be used for follow-up Positive Ab – patient has Ab to H. pylori – doesn’t necessarily mean existing symptoms due to H. pylori. In the absence of prior treatment, test likely indicates infection If no symptoms does not differentiate between active and past infection Negative Ab – indicates no Ab, specimen collected too early, impaired immune response
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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
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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
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Diagnosis of HIV Culture Rarely performed Serology - Gold Standard
Sensitive EIA Confirmatory Western blot Window period P24 antigen PCR
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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
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Diagnosis of HIV - POCT 1 CLIA “waived” test
OraQuick Rapid HIV-1 Antibody Test
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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:
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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 4 Chicago hospitals All rapid results confirmed by conventional testing 3 HIV+ all treated, 0 babies got HIV MMWR 2003; 52:
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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
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Diagnosis of HIV - POCT Advantages Disadvantages Rapid results
Counseling Rx Internal controls Accurate Disadvantages Must confirm positive results “Restrictions”
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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
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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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Provider Performed Microscopy
Things to think about… Training and continued proficiency Pictures Use of “live” specimens Microscope
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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
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