Transcript 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
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
