The Current Status of Influenza Testing 9.25.15.pdfStatistics of influenza and pneumonia Influenza...
Transcript of The Current Status of Influenza Testing 9.25.15.pdfStatistics of influenza and pneumonia Influenza...
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The Current Status of Influenza Testing
Norman Moore, PhD
Director of Scientific Affairs, Infectious Diseases
0
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Objectives
Discuss the health impacts of influenza in the US
Discuss the diagnostic options available for influenza
Discuss the biology of how an influenza infection can predispose a person to pneumococcal pneumonia
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Infectious Disease in the US
1970: William Stewart, the Surgeon General of the United States declared the U.S. was “ready to close the book on infectious disease as a major health threat”; modern antibiotics, vaccination, and sanitation methods had done the job.
1995: Infectious disease had again become the third leading cause of death, and its incidence is still growing!
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Treating Respiratory Diseases in the Emergency
Department
Is the pathogen bacterial or
viral?
Influenza and pneumonia
symptoms can overlap
dramatically
Who do you test?
If it is flu season, do you test for
other pathogens?
What do you test them for?
Different age groups are linked
to different pathogens.
Can treatment be impacted if the appropriate testing is done?
Stop indiscriminate
use broad spectrum
antibiotics.
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Misuse of Antibiotics Can Lead to Other
Medical Issues
Pneumonia may be treated with fluoroquinolone
Disrupts normal intestinal flora
O27 strain of C. difficile is specifically resistant to
fluoroquinolone
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Influenza A&B
Impact of influenza in the US
• Hospitalizations up from 114,000 to 226,000
• 36,000 deaths annually
• Influenza target population: 188MM in US
5-20% of US population affected by influenza each year
Most deaths affect elderly and young children
• Also affects otherwise healthy individuals
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The old thinking. . . “it’s just the flu”
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A bit of history
There are flu epidemics every 1 to 3 years for at least the last 400 years.
Pandemics (worldwide) occur around every 10 to 20 years.
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History
Hippocrates described flu back in the 5th century.
Columbus brought a devastating flu on his second voyage to the new world.
Spanish flu of 1918-1919 was the single greatest epidemic in history.
• 50 to 100 million people were killed (3-6% of the world’s population!)
• Another 500 million were infected (1/3rd of the world’s population)
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Aren’t you supposed to build immunity
to influenza?
The problem with influenza,
like the common cold, is that
there are many different strains.
That is also why the performance of rapid tests are
different every year!
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Influenza A versus Influenza B
Influenza A
• More severe disease than B
• Can cause disease in a wide variety of animals
Influenza B
• Causes a milder flu, usually in the spring months
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What rapid tests targets
Detecting influenza A and influenza B nucleoproteins (Ag)
The nucleoproteins are conserved throughout a given species
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So what is with the H and N?
H stands for hemagglutinin
• Allows virus to stick to cells
• Around 13 types
N stands for neuraminidase
• Helps release new virus from cells
• Around 9 types
Influenza A types have designations like H5N1, while influenza B viruses don’t
“Novel H1N1” is the same as swine flu
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Symptoms of Influenza Fever
Headache
Extreme tiredness
Dry cough
Sore throat
Runny nose
Muscle aches
Can also have – nausea, vomiting, and diarrhea
• This has been more common with the novel H1N1
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Infants Children Adults Novel H1N1
Fever ++ +++ +++ +++
Cough + ++ +++ +++
Myalgias - + ++ ++
Sore throat - + ++ ++
Headache - ++ ++ ++
Diarrhea ++ + - +
Vomiting ++ + - +
Rhinitis ++ + + +
Malaise ++ + + +
/ lethargy
Neurologic + - - +
symptoms
_________________________________________________
- rare, + uncommon, ++ common, +++ very common
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Influenza symptoms are ambiguous
Is it a very serious cold that you don’t treat?
Is it pneumonia that you treat with antibiotics?
Research by Aleta Bonner showed that there was a cost savings by running rapid influenza tests on patients.
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Results – Cost Savings
Associated with using a Rapid Test
Flu positive
MD aware
N=96
MD unaware
N=106
P value
CBC 0 13 <0.001
Blood Culture 0 11 <0.001
Urine dipstick 4 7 0.543
Urinalysis 2 12 0.011
Urine culture 3 14 0.011
CSF studies/culture 0 2 0.499
Chest X-ray 7 26 0.001
Lab/radiology
charges per patient
$15.65 $92.37 <0.001
Antibiotics 7 26 <0.001
Antivirals 18 7 0.02
Time (min. from
exam to discharge)
25 49 <0.001
Flu negative
MD aware
N=97
MD unaware
N=92
P value
13 7 0.196
12 6 0.172
7 7 0.918
10 8 0.706
12 5 0.096
3 2 0.695
22 23 0.708
$93.07 $68.91 0.871
27 27 0.818
0 2 0.236
45 42 0.549
Bonner, et al, Pediatrics (2003) 112:363-367
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Pediatric Study
Children who were positive by a rapid influenza test were;
• More likely to be prescribed an antiviral.
• Less likely prescribed an antibiotic.
• Jennings et al. “Effect of Rapid Influenza Testing on the Clinical Management of Paediatric Influenza.”
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Spread of Influenza
Flu is spread person-to-person through coughing or sneezing.
• Quick incubation of around 2 days
Hands can spread influenza if the person then touches their nose.
Healthy adults can infect others one day BEFORE symptoms develop and up to 5-7 days after.
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Viral Shedding
Shedding can begin 1 day before sickness
Peak of the shedding is within first 3 days of illness
Subsides around 5-7 days
• Can be longer in children
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Treatment
Nothing
Antiviral treatment
• Who gets priority for antiviral treatment?
• People who are hospitalized
• Under the age of 2 or over the age of 65
• Pregnant women
• Particular chronic or immunosuppressive conditions
• People under 19 who are receiving long-term aspirin therapy
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Treatment
2008-2009 season Influenza A was approximately 97% resistant to Tamiflu
The novel H1N1 was mostly sensitive to Tamiflu
Next year?
• What strains are in the population?
• Potential combination therapy
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Treatment – The other big issue
Antiviral drugs should be given within the first 48 hours of illness.
Some people don’t go in on the first day of symptoms.
Therefore, the treatment window can be small.
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How the virus changes – Shift vs. Drift
Antigenic drift – small changes in the virus that happen over time. It allows new strains that can evade the body’s immune system.
Antigenic shift – an abrupt, major change that results in a new hemagglutinin and/or new hemagglutinin and neuraminidase protein.
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How do you make a pandemic flu?
Avian H3 Human H2
Human H3
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Risk factors for severe disease with
novel H1N1
- Overall, similar to risk factors for seasonal influenza
- Chronic medical conditions including cardiopulmonary disease and immunosuppression
- Pregnancy
- neurodevelopmental delay
- Obesity (this is not recognized as a risk factor for seasonal influenza)
- Extremes of age have not been a risk factor for H1N1
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Natural protection against H1N1
Not
Protected
Protected
Older adults have natural protection from H1N1
J.A. McCullers
Unpublished
research
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Specimen Collection
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Influenza Sample Collection
• Nasal wash/aspirate, nasopharyngeal swab, or nasal swab
• Throat swabs have dramatically reduced sensitivity
Appropriate specimens
Samples should be collected within first 24 to 48 hours of symptoms since that is when viral titers
are highest and antiviral therapy is effective
• Infectivity is maintained up to 5 days when stored @ 4-8°C
• If the sample cannot be evaluated in this time period, the sample should be frozen @ -70°C.
Testing can be done immediately with rapids or sample
placed in transport media
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Diagnostic Methods for Influenza
Culture
DFA
PCR
Rapid Tests
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Viral Culture
Pro
• Highly sensitive as long as sample is properly handled
Con
• Can’t give same day result to help monitor therapy
• High level of difficult/equipment
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DFA
Pro
• Usually considered to have high level of sensitivity
• Can usually test for other respiratory pathogens at the same time
• Results can be achieved in same day
Con
• Labor intensive needed experienced users
• Turn-around time from lab usually takes many hours
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Molecular Assays
Pro
• For respiratory specimens, high performance
• Same day results
Con
• Turn around time from lab may be extensive, especially if batching specimens
• Expensive
• May require experienced technicians, labs, dedicated equipment, etc.
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Rapid Tests
Pro
• Tests take minimal time
• Some tests are so simple that they can be CLIA-waived
• Can be used to triage patients
• Positive results can be used to rule out other issues like pneumonia so don’t give unnecessary chest x-ray, antibiotics, etc.
Con
• Performance is not as good as culture, PCR, and DFA
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RAPID MOLECULAR TESTS
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The Power of Sample Amplification
Detection
threshold
Amplified
Flu+ Sample
Not Amplified
Flu+ Sample
Amplify the sample up to 1 trillion times!
Without amplification, a positive test might
not be detected.
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CDC Website Creates a New Diagnostic
Category http://www.cdc.gov/flu/professionals/diagnosis/molecular-assays.htm
36
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IMMUNOASSAY MOLECULAR
RAPIDS LAT FLOW
READERS PCR Rapid
FAST
CONVENIENT
POC-FRIENDLY
ACTIONABLE
RESULTS
REMOVES
SUBJECTIVITY
CONNECTED
EXCELLENT
PERFORMANCE
Technology Comparison
CONFIDENTIAL
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Better Care
Lower cost
Better Health
Healthcare’s “Triple Aim”
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Better Health
Better Health (Clinical)
Detect more true positives than gold standard
Increased confidence in diagnosis may lead to
better directed therapy
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Better Care (Operational)
Better Care
Confidently make appropriate clinical decisions
sooner
Molecular results in the time of a rapid assay
Actionable results at the point of care
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Lower Cost (Economic)
Limit number of cultures being done
Reduce follow-up burden on staff
More rapid discharge/treatment decision compared
to traditional testing
Lower cost
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Sensitivity vs Specificity vs
PPV vs NPV
Sensitivity:
Probability test=positive if patient=positive
Specificity:
Probability test=negative if patient=negative
PPV: Probability patient=positive if test=positive
NPV: Probability patient=negative if test=negative
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Flu is seasonal. Prevalence of the disease is different in June than
in January.
This will impact the perceived performance of the test
Test 1,000 persons
Test Specificity = 99.6% (4/1000)
Prevalence = 10%
True positive: False positive:
Positive predictive value: 100/104 = 96%
100 4
www.cdc.gov/hiv/rapid_testing
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Test 1,000 persons
Test Specificity = 99.6% (4/1000) Prevalence = 10%
True positive: 100 False positive: 4 Positive predictive value: 100/104 = 96%
Prevalence = 0.4%
True positive: 4 False positive: 4
Positive predictive value: 4/8 = 50%
www.cdc.gov/hiv/rapid_testing
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The Connection Between Influenza
and S. pneumoniae
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Statistics of influenza and pneumonia
Influenza pandemics of 1957 and 1968
• Bacterial etiology in roughly 70% of patients with severe pneumonia (life threatening or fatal)1,2
Influenza hospitalizations rates (non pandemic)
• 44-57% bacterial pneumonia3-6
Approximately 25% of influenza-related deaths have a secondary bacterial pneumonia7
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EID - Predictors of Pneumococcal Co-
infection with Pandemic (H1N1)
• Looked at adults who had influenza-like illness and sought medical attention and had ≥ 1 risk factor for contracting influenza-related complications
Study in
Spain July
2009- March 2010.
Emerging Infectious Diseases. www.cdc.gov/eid. Vol 17 1475-8.
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EID Study- Data Collection
• Oropharyngeal and nasopharyngeal swab samples
• Urine sample
• Sputum and 2 blood cultures
Samples
• PCR for the detection of influenza
• Blood, urinary antigen, or qualified sputum for S. pneumoniae
Assays
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EID Study - Results
• 179 were confirmed H1N1
• In PCR H1N1 negative, 25.1% had pneumococcal disease
418 patients
were evaluated
• 14% had pneumococcal infection
• “Infection in more than half these patients would not have been diagnosed if a pneumococcal urinary antigen test had not been performed.”
Of 100 patients
with influenza
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EID Study
When Coinfection Found. . .
Patients more frequently admitted to the hospital and to the intensive care unit
Had lower oxygen saturation
Had higher axillary temperature
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EID Study - Conclusions
Concurrent infection significantly increased risk of patient complications
If only looking for influenza, pneumococcal pneumonia may be missed or only looking for pneumonia, influenza may be missed.
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H1N1 Pandemic with S. pneumoniae in
Argentina1
• Similar to seasonal influenza
May 2009 – pandemic H1N1 had estimated
fatality rate of 0.6%
• No genetic difference in virus
• S. pneumoniae associated with 56.4% of severe disease
July 2009 – Argentina
reported fatality rate of 4.5%
(137 deaths out of 3056 cases)
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Proposed Mechanisms
Bacterial adherence after epithelial destruction
• Autopsy evidence in 1918 outbreak with S. aureus1
Neutrophil apoptosis in presence of influenza and S. pneumoniae2
Upregulation of molecules that S. pneumoniae can use as receptors
• Incubation with cytokines from viral infections3
Environmental factors
• High temperature, ATP, norepinephrine
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Conclusions
Diagnostic technologies for respiratory infections allow more directed therapy
Biological mechanisms do exist which predispose patients with influenza to pathogens such as S. pneumoniae
A superinfection with bacterial pneumonia has been shown to increase morbidity/mortality in influenza infections
Testing for both influenza and bacterial pneumonia in select populations can help predict how well patients do