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Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 1
Experts on Xpert:A laboratorian and a clinician discuss
interpretation of Xpert MTB/RIF Results
Pennan Barry, MD, MPHGrace Lin, MS
September 26, 2018
Curry International Tuberculosis Center
Learning Objectives
By the end of the training, participants will be able to:
• describe the principles behind the Xpert MTB/RIF test
• identify circumstances that should trigger additional testing or where false identification of MTB/RIF resistance should be suspected
• identify probes that most frequently detect mutations conferring RIF resistance and silent mutations not conferring RIF resistance
• identify situations where additional Xpert testing is not indicated
Xpert interpretatiom-Curry Center-9/26/18 2
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 2
Disclosures
• None
Xpert interpretatiom-Curry Center-9/26/18 3
Agenda
• Intro: – Not an introduction to Xpert use
– Not about release from respiratory isolation
• What is Xpert and how does it work?
• Case discussions:– Illustrate nuances of Xpert interpretation
(focus on RIF resistance result)
– When to ask for more info or more testing
– When not to test more
4Xpert interpretatiom-Curry Center-9/26/18
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 3
Xpert MTB/RIF assay
• Great tool for TB detection• FDA Approved• Shortens time significantly • Testing time 2.5 hr; Easy to perform• Real-Time PCR
– 5 molecular beacon probes– rpoB gene (core region, codons 507-533)
5
Xpert Clinical Report
Xpert interpretatiom-Curry Center-9/26/18 6
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 4
“Hidden” Info: Report on Xpert computer
Xpert interpretatiom-Curry Center-9/26/18 7
Methodology: Realtime PCR
• Realtime PCR = PCR + probes
• PCR = Polymerase Chain Reaction– Generates copies of specific segments
of DNA
– DNA copies double with each PCR cycle
• Probes report whether specific sequence is present– Probes bind to amplicons; generate
signals with each PCR cycle
Xpert interpretatiom-Curry Center-9/26/18 8
PCR cycles
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 5
PCR Cycles
https://www.khanacademy.org/science/biology/biotech-dna-technology/dna-sequencing-pcr-electrophoresis/a/polymerase-chain-reaction-pcr
9
10
Molecular Beacon probe(Hairpin structure—head & two arms)
Head (functional part, MTBC sequence, ~20 nt)
Two arms (5-7 nt)
Fluorophore Quencher
At “rest” stage, two arms bind together forming a stem.Fluorophore is quenched. No signals are produced.
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 6
11
MB head does not bind to mutant SQ.Arms remain closed.No signals produced.
Mutation Detection with Molecular Beacons (Head containing wildtype SQ)
Mutant Sequence Wildtype Sequence
MB in action!MB resting
MB head binds to wildtype SQ.Arms open. Fluorophore away from quencher. Signals produced.
Ct: Threshold Cycleat which signal crosses threshold Low DNA in the specimen High Ct
0
250
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
Flu
ore
sce
nce
p
rod
uce
d b
y p
rob
e b
ind
ing
PCR Cycle
Threshold
12
Sample 1 (Wildtype)
Ct=18
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 7
Ct: Threshold Cycleat which signal crosses threshold Low DNA in the specimen High Ct
0
250
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
Flu
ore
sce
nce
p
rod
uce
d b
y p
rob
e b
ind
ing
PCR Cycle
Threshold
13
Sample 1 (Wildtype)
Sample 2 (Wildtype)
Ct=18 Ct=25
Ct: Threshold Cycleat which signal crosses threshold Low DNA in the specimen High Ct
0
250
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
Flu
ore
sce
nce
p
rod
uce
d b
y p
rob
e b
ind
ing
PCR Cycle
Threshold
14
Sample 1 (Wildtype)
Sample 2 (Wildtype)
Sample 3
Ct=18 Ct=25
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 8
No signals: 3 possibilities
• Mutation(s) present
• MTBC DNA insufficient or not present
– Smear-negatives (if < ~120 colonies/mL)
• Unable to generate enough DNA copies
– Smear positive but not MTBC
• Inhibitory substance
– Inhibit amplification
– Xpert has internal control (SPC) to detect this
• Signals in SPC indicate no inhibitory substance in specimen
Xpert interpretatiom-Curry Center-9/26/18 15
Critical Rules for Interpretation(Set by the Xpert software)
• MTBC detected
– at least 2 probes are positive
• RIF-R detected
– If highest and lowest Ct differs by more than 4 (Δ Ct max > 4)
• See more rules in package insert
16
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 9
Typical Xpert results
(Examples showing Xpert’s rules work as intended -- No nuance!)
17
18
Ct End-pt MTBC: Not detected
• No probe has signal
• SPC has signal. If no signal, test is invalid.
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 10
19
MTBC detected• 5 probes up
RIF-SNo mutation• Δ Ct max < 4
(33.9-31.8=2.1)
Ct End-ptCt End-pt
20
MTBC detected• 4 probes upRIF-R detected• Probe E no signals
Δ Ct max > 4:24.8-0=24.8
• Most common MDR mutation: S531L, detected by probe E
Ct End-ptCt End-pt
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 11
Xpert Probes: Coverage of rpoB
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
Codon#
Most common mutation confers
resistance (531 TTG)
Ask your lab which probe resulted in the RIF-R result
21
Can Xpert differentiateM. tuberculosis (MTB) from
M. tuberculosis complex (MTBC)?
Xpert interpretatiom-Curry Center-9/26/18 22
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 12
M. tuberculosis Complex
• M. tuberculosis
• M. bovis
• M. africanum
• M. caprae
• M. pinnipedii
• M. microti• M. mungi, M. orygis, M.
canettii, M. suricattae(proposed)
Xpert interpretatiom-Curry Center-9/26/18 23
All cause tuberculosis
MTB / MTB Complex?
• Species in the MTB complex have same rpoBcore region sequence
– Xpert can only identify MTBC, not MTB species.
• “MTBC” is the correct term.
• Xpert results for M. tuberculosis and M. bovisindistinguishable
24
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 13
Complications encountered in the real
world TB clinicApply your new knowledge of the
“hidden info” on the Xpert computer
Xpert interpretatiom-Curry Center-9/26/18 25
The problems
• Silent mutations – Xpert software does not know they are silent
– Interprets as RIF-R
• Smear-negatives (low MTBC DNA)– May falsely detect RIF-R
– May falsely identify NTM as MTBC [rare]
• Dead bugs– Xpert finds DNA; cannot distinguish between
alive and dead organisms
Xpert interpretatiom-Curry Center-9/26/18 26
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 14
Case 1
• 70 yo man born in Mexico
• Cough, wt loss, night sweats x 2 months
• CXR shows left upper lobe infiltrate
• Sputum is smear positive
• Xpert is ordered
Xpert interpretatiom-Curry Center-9/26/18 27
28
MTBC detected• 4 probes up RIF-R detected• Probe B (no signals)Caution:• Most common Silent
mutation in probe B
Ct End-ptCt Ct End-pt
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 15
Xpert Probes: Coverage of rpoB
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
Codon#
Most common silent mutation
(514 TTT)
Ask your lab which probe resulted in the RIF-R result
29
Big surprise!
• ~20% of all the mutations detected in the rpoB
core region are Silent!(In California and other low MDR areas)
• Most common is 514TTT
• Mutations detectable by probe B:– 70% is this silent mutation
– Disputed mutation: 516TAC, 516TTC,
– RIF-R mutations: 516GTC, 513AAA, GAA, etc.
• Pennan, how to deal with probe B mutations?
Xpert interpretatiom-Curry Center-9/26/18 30
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 16
Number and Proportion MDR-TB by Country/Region of Origin, CA 2011–2015
• Countries with >35 cases tested for MDR
Country/Region No. %Former Soviet Republics 5 12.2
Laos 6 5.1
Burma 2 3.4
India 12 3.1
Guatemala 5 3.0
Korea (N&S) 7 2.9
Peru 1 2.6
Ethiopia 1 2.0
Philippines 27 1.7
Vietnam 13 1.4
China (incl Taiwan) 7 1.2
United States 13 0.8
Cambodia 1 0.7
Mexico 11 0.6
31
Number and Proportion MDR-TB by Country/Region of Origin, CA 2011–2015
• Countries with >35 cases tested for MDR
Country/Region No. %
PPV (99% spec)
PPV (98% spec)
Former Soviet Republics 5 12.2 93% 87%
Laos 6 5.1 84% 72%
Burma 2 3.4 77% 63%
India 12 3.1 75% 60%
Guatemala 5 3.0 75% 60%
Korea (N&S) 7 2.9 74% 59%
Peru 1 2.6 72% 56%
Ethiopia 1 2.0 66% 50%
Philippines 27 1.7 62% 45%
Vietnam 13 1.4 57% 40%
China (incl Taiwan) 7 1.2 54% 37%
United States 13 0.8 44% 28%
Cambodia 1 0.7 40% 25%
Mexico 11 0.6 36% 22%
32
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 17
MDR-TB Cases by Country/Region of Origin and Years in the US, CA 2011–2015
Country/Region
TotalMDR TB
cases
≤ 2 years in US
No. (%)>2 years in US
No. (%)
All Countries* (excl U.S.)
103 30 (3.7) 71 (1.2)
Vietnam* 13 9 (7.9) 3 (0.4)
China*(incl Taiwan)
7 5 (8.8) 2 (0.4)
Philippines* 27 8 (4.0) 19 (1.4)
* Difference is statistically significant 33
Order Xpert or PSQ for Patients with MDR Risk!
MDR risks:
• Prior TB treatment
• Contact to patient with drug resistant TB
• Non-U.S.-born from country with increased MDR risk (≥2% MDR among TB cases in California)
• Arriver to U.S. within 2 years
• HIV positive
Among 42 smear positive MDR cases with MDR risk, 20 did not get Xpert or PSQ on sputum (California, 2012-2016)
34Lowenthal, NTCA/CTCA poster 2018
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 18
Probe B Interpretation
• Interpret in clinical context
– Are there risks for DR TB?
– Is there a pressing need to start treatment immediately?
• In this case: born in Mexico, no prior treatment, not a contact probably silent
• Pyrosequencing: 514TTT (Silent mutation)
35
36
Testing smear-negative samples
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 19
Case 2
• 30s yo F cough x 4 weeks
• No prior TB treatment
• Born in country with low MDR prevalence; no travel
• Household contact to pan-S case 1 year prior
Xpert interpretatiom-Curry Center-9/26/18 37
MTBC DetectedRIF-R detectedHigh CtsΔCt = 33.8-29.7 = 4.1
38
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 20
39
MTBC DetectedRIF-R not detectedHigh CtsΔCt = 31.1-28.2 = 2.9
Case 2
• Treated with RIPE
• Clinically improved after 1 week
• Pyrosequencing: no amplification
• DSTs: PanS
Xpert interpretatiom-Curry Center-9/26/18 40
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 21
Xpert MTB/RIF Performanceon Smear Negative Sputum Compared with
Culture, U.S. patients
Sensitivity Specificity
1 Xpert 2 Xperts
59.3%(16/27)
71.4%(20/28)
99.2%
Luetkemeyer Clin Infect Dis 2016 41
• Should we always test two samples?
Case 3
• 50 yo man born in Mexico, in U.S. for 10 yrs
• 6 weeks of cough, night sweats
• CXR RUL nodular infiltrate
• No MDR contact, no prior treatment
• All smears are negative
• Xpert pending
– Order testing 2 samples to increase sensitivity!?
42
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 22
Xpert interpretatiom-Curry Center-9/26/18 43
Sample #1 Sample # 2
Conflicting results! Shall I worry false positivity?Ask lab to test another specimen!?
MTBC not detected
MTBC detectedRif Resistance not detected
44
Sample 3 Sample 4
Sample #3 results were indeterminate. Order another test!!Sample #4 results were RIF-R.Hit the jackpot! 4 tests 4 different results!
MTBC detected Rif resistance indeterminate
MTBC detectedRif resistance detected
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 23
Problems with testing smear-negatives
• MTBC DNA – Low, very low or not present
– Xpert’s detection limit is about 120 CFU/mL
• Xpert results less reproducible, because:– Reduced amplification: generate fewer amplicons
• PCR efficacy varies between runs
– Reduced probe binding: generate less signals • Probe’s binding efficacy varies more among probes
• Increased Δ Ct max: Increased false RIF-R detection
Xpert interpretatiom-Curry Center-9/26/18 45
Follow-up actions• MTBC not detected
– Does not rule out MTBC. Consider second Xpert– Wait for culture results.
• MTBC detectedRifampin resistance not detected– Most reliable
• MTBC detectedRifampin resistance detected– Need to be confirmed by sequencing.
• MTBC detectedRifampin resistance indeterminate [not discussed today]– Likely happens when testing smear-negatives.– If this is a first test, test 2nd specimen. – If this is a 2nd test. Wait for culture results.
Xpert interpretatiom-Curry Center-9/26/18 46
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 24
Two probes positive = MTBC?
• This is a dangerous rule!– Especially when the sample is smear-negative
• Two probes pos = 3 or more mutations– Very RARE to have ≥ 3 mutations within 81 bp
– Out of 3754 tested, 2 samples had 3 mutations (MDL data)• None detected by 3 probes!
• One detected by 2 probes (A & B)
• One detected by 1 probe (D)
Xpert interpretatiom-Curry Center-9/26/18 47
When should NTM be suspected?
• Smear-negative
– Only two probes are positive. Xpert reports MTBC and RIF-R detected.
• Smear-positive
– Multiple Xperts: MTBC not detected
Xpert interpretatiom-Curry Center-9/26/18 48
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 25
Can we use Xpert for detection of relapses?
Xpert interpretatiom-Curry Center-9/26/18 49
Case 4
• 70 yo man from China
• 5 years ago treated for cavitary TB with RIPEcured
• Presents to ED with 2 days of SOB, no fever, night sweats or weight loss (weight gain)
• CXR with bilateral pleural effusions
• Smear neg, Xpert positive, RIF-R (Probe A)
• No sequence detected by PSQ
• Culture grew a rapid grower
• DNA of the isolate from 5 years ago, showed rpoB 511 CCG (detectable by probe A)
50Kelly et al Am J Resp Crit Care Med 2014
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 26
Case 4
• History concerning for MDR
• Clinical presentation atypical for TB, more compatible with CHF
• Treated for 2 weeks then stopped
• All cultures negative, including 12 mos later
• Negative cultures and same rpoB mutation as prior --> dead bugs?
51Kelly et al Am J Resp Crit Care Med 2014
Xpert positivity on treatment
• Insert figure from publication…
Friedrich, Lancet Respir Med 2013; 1: 462–70
Weeks after treatment initiation
27%
52
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 27
Don’t get Xpert after treatment start or in previously treated patients
• Xpert cannot determine alive vs dead
• Xpert can remain positive for years after curative treatment
• Package insert recommends against Xpert in anyone treated for >3 days
• If you order it, only helpful if different RIF result from prior (e.g., a previously pan-S case has a probe E RIF-R result)
53
Summary Points
• Order Xpert!
• If results surprise you, talk to your lab!– Ask for probe and Ct info
• Interpret in clinical context– How likely is it that this patient has TB and DR-TB?
• MDR risk factors? Prior treatment, contact to MDR case, born in country with high MDR prevalence?
– Can you wait for culture results?
• Get rpoB sequencing for all RIF-R specimens– If smear negative (Ct > 28), wait for culture
Xpert interpretatiom-Curry Center-9/26/18 54
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 28
Acknowledgments• Ed Desmond
• Phil Lowenthal
• Neha Shah
• MDR Service
• Microbial Disease Lab
55
Pennan Barry
Gayle Schack
(Ret)
Kristen Wendorf
Lisa True
Phil Lowenthal
Jenny Flood
LeslieHenry
Neha Shah
Not pictured: Shereen Katrak
Christy Pak (Ret)
Wendy Cheung
Grace Lin
Lucy Pham
Terry Weber
Stephen Yu
• Zachraias Zachraias
• Kitty Reiher
• Amelia Alonis
Thank You!
• pennan.barry@cdph.ca.gov
• grace.lin@cdph.ca.gov
Xpert interpretatiom-Curry Center-9/26/18 56
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 29
Resources
• California Microbial Diseases Lab PSQ: https://www.cdph.ca.gov/Programs/CID/DCDC/CDPH%20Document%20Library/MDL-Pyrosequencing-for-XDR-TB-Screening.pdf
• Curry/CDPH MDR TB Survival Guide Lab Chapter: http://www.currytbcenter.ucsf.edu/products/drug-resistant-tuberculosis-survival-guide-clinicians-3rd-edition/chapter-3-laboratory
• CDC TB Lab: https://www.cdc.gov/tb/topic/laboratory/default.htm
• NTCA/APHL Consensus Statement on Xpert for release from isolation: http://www.tbcontrollers.org/docs/resources/NTCA_APHL_GeneXpert_Consensus_Statement_Final.pdf
• Khan academy PCR unit: https://www.khanacademy.org/science/biology/biotech-dna-technology/dna-
sequencing-pcr-electrophoresis/a/polymerase-chain-reaction-pcr
• Xpert MTB/RIF Package Insert: http://www.cepheid.com/administrator/components/com_productcatalog/library-files/f625a0c86cd73ce46ba391c24a3eabc4-3a9ca7ef6b9b88dc736e5a437f41eb3a-Xpert-MTBRIF-ENGLISH-PackageInsert-301-1404-Rev-C.pdf
57
rpoB Facts
• Most common mutation conferring RIF-R
– rpoB 531TTG—detectable by Probe E
• 2nd most common mutation conferring RIF-R
– rpoB 526TAC & 526GAC—detectable by probe D
• Most common silent mutation
– rpoB 514TTT—detectable by probe B (>20% of all mutations)
• Disputed mutations are not common, but are detectable
– But you would not know unless sequenced.
• Not common to have 2 mutations, very rare to have 3 mutations. Even more rare to have 3 mutations detected by 3 probes.
58
Experts on Xpert: A Laboratorian and a Clinician Discuss Interpretation of Xpert MTB/RIF ResultsDr. Pennan Barry (MD, MPH) and Grace Lin (MS)
September 26, 2018 30
rpoB codon numbering change
• Historically rpoB codons numbered with E. coliAll other loci numbered according to M. tuberculosis
• Change to M. tuberculosis numbering to align with whole genome sequencing data
• Good news: just subtract 81
– 531 450 526 445 514 433 516 435
• MDL has started using MTBC numbering (As of 8/1/18)
– Codon conversion info provided in comment
Xpert interpretatiom-Curry Center-9/26/18 59
Xpert Ultra
• WHO recommends the use of Ultra.
• 2 specific targets for detection of MTBC– IS6110 & IS1081
• Increased sensitivity for MTBC detection– 66% (G4) vs 79% (Ultra)
• Added a step to analyze melting temperature for identification of specific mutations.– 4 “sloppy” MB probes for detecting rpoB mutations.
– F514F Silent mutation is not detected. Great news!
60
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