HPPA 6294 Evidence Based Medicine I
Article Appraisal 1 & 2– Methods, Diagnosis Article Results
Name:
For this assignment, you will begin to practice article appraisal of the research methods and
results of selected articles. It is recognized you have basic overview of the concepts. You are
encouraged to use higher order thinking with the concepts presented and practical application
to patient care to answer the questions provided.
Grading: Refer to the rubric tab connected to the assignment on Sakai.
Article 1 Instructions: The purpose of the first article appraisal is to specifically look at study
methodology related to study design. It is recommended for you to read the questions
alongside of the article to respond to each. If it not necessary to interpret the results of this
study.
Article for Appraisal –
DISCHARGE Trial Group; Maurovich-Horvat P, Bosserdt M, Kofoed KF, et al. CT or Invasive
Coronary Angiography in Stable Chest Pain. N Engl J Med. 2022 Apr 28;386(17):1591-1602. doi:
10.1056/NEJMoa2200963. Epub 2022 Mar 4. PMID: 35240010.
Answer the following questions:
Study Type: Randomized Controlled Trial
1. Did the study address a clearly focused research question?
Yes
No
Can’t Tell
Complete the following information:
* Population studied? Patients experiencing stable angina.
* Intervention given? Computed tomography (CT).
* Comparator chosen? Invasive coronary angiography (ICA).
* Outcomes measured? There were major cardiovascular events in 2.1% in the CT
group compared to 3% in the ICA group. There were major procedural related conditions in
0.5% in the CT group versus 1.9% in the ICA group. As well as, angina occurring in 8.8% of the
CT group in the following 4 weeks versus 7.5% in the ICA group.
2. Was the assignment of participants to interventions randomized?
Yes
No
Can’t Tell
Complete the following information:
* How was randomization carried out and was it appropriate? Randomization was
evenly selected by a web-based system at a 1:1 ratio of either CT or ICA. It was appropriate.
* Was randomization sufficient to eliminate systematic bias? Yes. The web-based
system concealed all group assignments.
HPPA 6294 Evidence Based Medicine I
Article Appraisal 1 & 2– Methods, Diagnosis Article Results
* Was the allocation sequence concealed from investigators and participants? Yes. The
web-based system concealed the assignment sequence until after all eligibility criteria had
been verified.
3. Were all participants who entered the study accounted for at its conclusion?
Yes
No
Can’t Tell
Complete the following information:
* Were losses to follow-up and exclusions after randomization accounted for?
* Were participants analyzed in the study groups to which they were randomized?
* Was the study stopped early? If so, what was the reason?
4. Were the study groups similar at the start of the study?
Yes
No
Can’t Tell
Complete the following information:
* Were the baseline characteristics of each study group (age, gender, socio-economic
group, etc.) clearly set out? (hint: see Table 1)
* Were there any differences between the study groups that could affect the outcome/s?
5. Apart from the experimental intervention, did each study group receive the same level of
care (that is, treated equally)?
Yes
No
Can’t Tell
Complete the following information:
* Was there a clearly designed protocol for the study?
* If any additional interventions were given, were they similar between study groups?
* Were the follow-up intervals the same for each study group?
Article 2: The purpose of the second article appraisal is to apply the concepts of sensitivity and
specificity, predictive value, and likelihood ratios to patient care. It is recommended for you to
read the questions alongside of the article to respond to each. It is recognized we have not yet
covered details of confidence intervals. It is not necessary to address these as you look at the
results.
Article for appraisal: Yang TY, Huang L, Malwade S, Hsu CY, Chen YC. Diagnostic Accuracy of
Ambulatory Devices in Detecting Atrial Fibrillation: Systematic Review and Meta-analysis. JMIR
Mhealth Uhealth. 2021 Apr 9;9(4):e26167. doi: 10.2196/26167. PMID: 33835039; PMCID:
PMC8065566.
1. Did the study address a clearly focused research question?
Yes
No
Can’t Tell
Complete the following information:
HPPA 6294 Evidence Based Medicine I
Article Appraisal 1 & 2– Methods, Diagnosis Article Results
* Population studied?
* Intervention given?
* Comparator chosen?
* Outcomes measured?
2. Was the assignment of participants to interventions randomized?
Yes
No
Can’t Tell
Complete the following information:
* How was randomization carried out and was it appropriate?
* Was randomization sufficient to eliminate systematic bias?
* Was the allocation sequence concealed from investigators and participants?
3. Did the researchers use methods in the design to reduce bias, confounding variables, etc.?
Yes
No
Can’t Tell
Complete the following information:
*What strategies were used and were they appropriate?
*Are there sources of bias not accounted for within the study design or methods that
could affect the results?
4. Based on the sensitivity and specificity of the Facial Photoplethysmography vs. 12-Lead EKG,
is there a higher risk of false-positive or false negative results?
Yes
No
Can’t Tell
Complete the following information:
* Explain your reasoning for the answer above.
5. Explain the use of the PPV and NPV in determining the usefulness of photoplethysmography.
6. How would you recommend the use of facial photoplethysmographic signal to determine the
presence of AF in your patients? Why or why not?
Use it
Do not use it
Not sure
Include information about the sensitivity specificity, and likelihood ratio in your response.
new england
journal of medicine
The
April 28, 2022
established in 1812
vol. 386
no. 17
CT or Invasive Coronary Angiography in Stable Chest Pain
The DISCHARGE Trial Group
a bs t r ac t
BACKGROUND
In the diagnosis of obstructive coronary artery disease (CAD), computed tomography (CT) is an accurate, noninvasive alternative to invasive coronary angiography (ICA). However, the comparative effectiveness of CT and ICA in the management of CAD to reduce the frequency of major adverse cardiovascular events is
uncertain.
The authors’ full names, academic degrees, and affiliations are listed in the
Appendix. Dr. Dewey can be contacted at
marc.dewey@charite.de or at the Department of Radiology, Charité–Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
METHODS
Drs. Maurovich-Horvat, Bosserdt, and
Kofoed contributed equally to this article.
We conducted a pragmatic, randomized trial comparing CT with ICA as initial
diagnostic imaging strategies for guiding the treatment of patients with stable
chest pain who had an intermediate pretest probability of obstructive CAD and
were referred for ICA at one of 26 European centers. The primary outcome was
major adverse cardiovascular events (cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke) over 3.5 years. Key secondary outcomes were procedurerelated complications and angina pectoris.
This article was published on March 4,
2022, at NEJM.org.
N Engl J Med 2022;386:1591-602.
DOI: 10.1056/NEJMoa2200963
Copyright © 2022 Massachusetts Medical Society.
CME
at NEJM.org
RESULTS
Among 3561 patients (56.2% of whom were women), follow-up was complete for
3523 (98.9%). Major adverse cardiovascular events occurred in 38 of 1808 patients
(2.1%) in the CT group and in 52 of 1753 (3.0%) in the ICA group (hazard ratio,
0.70; 95% confidence interval [CI], 0.46 to 1.07; P = 0.10). Major procedure-related
complications occurred in 9 patients (0.5%) in the CT group and in 33 (1.9%) in
the ICA group (hazard ratio, 0.26; 95% CI, 0.13 to 0.55). Angina during the final
4 weeks of follow-up was reported in 8.8% of the patients in the CT group and in
7.5% of those in the ICA group (odds ratio, 1.17; 95% CI, 0.92 to 1.48).
CONCLUSIONS
Among patients referred for ICA because of stable chest pain and intermediate
pretest probability of CAD, the risk of major adverse cardiovascular events was
similar in the CT group and the ICA group. The frequency of major procedurerelated complications was lower with an initial CT strategy. (Funded by the European Union Seventh Framework Program and others; DISCHARGE ClinicalTrials
.gov number, NCT02400229.)
n engl j med 386;17
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T h e n e w e ng l a n d j o u r na l o f m e dic i n e
I
A Quick Take
is available at
NEJM.org
1592
n the diagnosis of obstructive coronary artery disease (CAD), computed tomography (CT) is an accurate, noninvasive alternative to invasive coronary angiography (ICA) in
patients with stable chest pain and intermediate
pretest probability for obstructive CAD.1,2 ICA is
the reference standard for the diagnosis of obstructive CAD and enables coronary revascularization during the same procedure. However,
elective ICA is associated with rare but major
procedure-related complications3 and has been
reported to reveal obstructive CAD in only 38 to
50% of the patients who are referred for the
procedure in the United States4 and Europe.5
CT has generated interest since it may rule out
obstructive CAD in a noninvasive procedure with
a low risk of adverse events as it identifies patients who are appropriate candidates for coronary revascularization.6 As compared with an
initial strategy of functional testing (exercise
electrocardiography, nuclear stress testing, or
stress echocardiography), an initial CT strategy
in patients with stable symptoms was associated
with similar cardiovascular outcomes at 25 months
in the PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) trial,
which indicated equipoise between functional
testing and CT.7,8 In the SCOT-HEART (Scottish
Computed Tomography of the Heart) trial, CT
was added to standard care, which included
functional testing, and was compared with standard care alone. The use of CT was associated
with a significantly lower incidence of major adverse cardiovascular events, which were defined
as death from CAD or nonfatal myocardial infarction at 4.8 years (hazard ratio, 0.59).9 In two
small randomized trials of CT as compared with
ICA,10,11 an initial CT strategy resulted in a lower
number of invasive procedures, a higher percentage (75%) of coronary angiograms showing obstructive CAD, and similar clinical outcomes,
which included hospitalization and revascularization.12
We conducted the DISCHARGE (Diagnostic
Imaging Strategies for Patients with Stable Chest
Pain and Intermediate Risk of Coronary Artery
Disease) trial to compare CT with ICA as an
initial diagnostic imaging strategy for guiding
the treatment of patients with stable chest pain
who were clinically referred for ICA. Here, we
report the comparative effectiveness of CT and
ICA in preventing the primary outcome of major
n engl j med 386;17
adverse cardiovascular events, defined as cardiovascular death, nonfatal myocardial infarction,
or nonfatal stroke.
Me thods
Trial Design and Oversight
We conducted this multicenter, pragmatic, randomized superiority trial to compare CT with
ICA in guideline-directed management of stable
chest pain.13-15 The trial design and methods have
been published previously16 and are described in
the protocol (which includes the statistical analysis plan) and the Supplementary Appendix (both
of which are available with the full text of this
article at NEJM.org). In brief, this investigatorinitiated, assessor-blinded, parallel-group trial
was reviewed and approved by the ethics committee at Charité–Universitätsmedizin Berlin as
the coordinating center, by the German Federal
Office for Radiation Protection, and by local or
national ethics committees. The trial was funded by the European Union Seventh Framework
Program and others. The authors vouch for the
accuracy and completeness of the data and for
the fidelity of the trial to the protocol. The second author and last author wrote the first draft
of the manuscript (see the Study Organization
section in the Supplementary Appendix).
Patients and Randomization
Eligible patients were at least 30 years of age and
were referred for ICA to one of 26 centers in 16
European countries because of stable chest pain
with intermediate (10 to 60%) pretest probability
of obstructive CAD. Referral for ICA with or without previous functional testing was in accordance
with the European guidelines at the time of trial
initiation.13,15 The pretest probability of obstructive CAD was assessed after enrollment but before randomization with a contemporary calculator according to the patient’s age, sex, and type
of chest pain (Section S7 in the Supplementary
Appendix). Clinical centers were informed by
means of the Web-based enrollment system
about whether the calculated pretest probability
was within the eligible range. Exclusion criteria
were the receipt of hemodialysis, an absence of
sinus rhythm, and pregnancy.
Patients were randomly assigned in a 1:1 ratio
to undergo either CT or ICA with the use of a
Web-based system to ensure concealment of
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CT or Coronary Angiogr aphy in Stable Chest Pain
group assignments after eligibility criteria had
been checked. Block randomization used computer-generated and randomly permuted blocks
of 4, 6, or 8, stratified according to center and
the patient’s sex with central assignment. All the
patients provided written informed consent.
Trial Procedures
CT and ICA were performed at certified clinical
centers (Section S9). CT with at least 64-slice
technology was performed according to a 10-step
guide and scanner-specific recommendations.16
CT scans were interpreted by board-certified
radiologists who had at least a level 2 qualification, according to the Society of Cardiovascular
Computed Tomography or similar certification,
and at least one reader had level 3 certification
for cardiac CT laboratory leadership. ICA was
performed according to contemporary guidelines
by board-certified cardiologists.17
In the two groups, it was recommended that
patients without obstructive CAD be discharged
from the trial center back to their referring physician for further treatment; patients with obstructive CAD were treated according to guidelines.13,15 Trial centers were provided with
recommendations incorporating European guidelines on the management of stable CAD,13 on
cardiovascular disease prevention,14 and on myocardial revascularization15 (Sections S10 and S11).
Decisions regarding treatment were made by
members of local heart teams and referring physicians on the basis of results on CT and ICA. In
the two groups, additional recommendations
included risk-factor modification and secondary
prevention,13 according to guidelines regarding
cardiovascular disease prevention.14 A CT-based
clinical management guideline was provided to
participating trial centers.
Outcomes
The primary outcome of major adverse cardiovascular events was a composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. In this pragmatic trial, we did not
assess myocardial biomarkers for the detection
of silent myocardial infarction or perform brain
imaging for the detection of asymptomatic
stroke after all procedures. Therefore, the trial
protocol required that the primary outcome be
symptomatic. Cardiovascular death was determined according to the criteria of the Cardiac
n engl j med 386;17
Safety Research Consortium, myocardial infarction was determined according to the Third Universal Definition of myocardial infarction, and
stroke was determined according to the updated
definition for the 21st century (Section S12).
Possible cardiovascular events were adjudicated
by members of an independent clinical events
committee, who were unaware of group assignments. We also evaluated an expanded primary
outcome that was a composite of cardiovascular
death, nonfatal myocardial infarction, nonfatal
stroke, transient ischemic attack, or major procedure-related complications.
Key secondary outcomes were major procedurerelated complications occurring during or within
48 hours after CT or ICA or related tests or revascularization procedures. Complications of ICA
or revascularization procedures that were performed after CT were attributed to the CT strategy and were classified according to the National
Cardiovascular Data Registry CathPCI Registry
Coder’s Data Dictionary, version 4.4. Patientreported outcomes included angina during the
last 4 weeks of follow-up, the score on the visualanalogue scale of the European Quality of Life–5
Dimensions (EQ-5D), and the score on the physical component summary of the Short-Form Health
Survey (SF-12v2). Additional secondary outcomes
were defined in the trial registration and statistical analysis plan but are not the topic of this
article (Section S16).
Statistical Analysis
We determined that the enrollment of 3546 patients would provide the trial with 80% power to
detect a relative reduction in the annual risk of
the primary outcome from 1.4% in the ICA group
to 0.8% in the CT group, assuming an annual
loss to follow-up of 5%. We used a sequential
design in which one interim analysis was performed after the occurrence of 50 major adverse
cardiovascular events. The two-sided P value was
set at 0.05, with levels of 0.0052 for the interim
analysis and 0.048 for the final analysis, according to the O’Brien–Fleming method. After review
and approval by the European Commission, the
enrollment period was extended from the planned
2 years to 3.5 years to enable the recruitment of
the planned number of patients, and the median
follow-up period was extended from 3 years to
3.5 years to maintain statistical power.
Analyses were performed in a modified inten-
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T h e n e w e ng l a n d j o u r na l o f m e dic i n e
Table 1. Characteristics of the Patients at Baseline.*
Characteristic
Median age (IQR) — yr
Female sex — no. (%)
Computed
Tomography
(N = 1808)
Invasive Coronary
Angiography
(N = 1753)
61.3 (53.2–67.8)
60.6 (53.0–67.4)
1019 (56.4)
983 (56.1)
1386/1752 (79.1)
1327/1695 (78.3)
Typical angina
232 (12.8)
275 (15.7)
Atypical angina
843 (46.6)
805 (45.9)
Nonanginal chest pain
677 (37.4)
634 (36.2)
Other
56 (3.1)
39 (2.2)
36.6 (28.8–46.2)
37.9 (29.5–46.5)
Clinical constellation suggesting high event risk, particularly with inadequate response to medical treatment
870/1802 (48.3)
791/1745 (45.3)
Severe angina, particularly with inadequate response to medical treatment
354/1802 (19.6)
397/1745 (22.8)
Intermediate pretest probability of CAD or LVEF 8.8 million adults worldwide.1
Prevalence of AF sharply increases with age, and with our
rapidly aging population, prevalence of AF is expected to
double by 2060.2,3 Cardioembolic stroke is one of the most
common complications of AF, and at least 1 in 3 strokes is
directly attributable to AF.4,5 One of the clinical challenges is
to identify AF and initiate stroke prophylaxis before the
occurrence of stroke. However, detection of AF can be
difficult because it is often asymptomatic and intermittent in
duration. In a recent study, AF was first diagnosed at the time
of stroke in nearly 1 in 5 cases.6
Screening can identify asymptomatic AF for stroke prophylaxis, but the best method of AF screening is not established. In
From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong and Prince of Wales Hospital,
Hong Kong SAR, China (B.P.Y., W.H.S.L., C.K.Y.C., O.T.L.T.); Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China (S.C.-H.C., L.-H.C.,
K.-M.L., H.-W.L., C.-M.N., L.-Y.T., K.-W.Y.); Heart Research Institute, Charles Perkins Centre, and Concord Hospital Cardiology, University of Sydney, Australia (B.F.); and
Cardiio Inc, Cambridge, MA (Y.C.P., M.-Z.P.).
An accompanying Figure S1 is available at http://jaha.ahajournals.org/content/7/8/e008585/DC1/embed/inline-supplementary-material-1.pdf
Preliminary work related to this study (Abstract 17351; Circulation. 2016;134:A17351-A) was presented at the American Heart Association Scientific Sessions,
November 12 to 16, 2016, in New Orleans, LA.
Correspondence to: Bryan P. Yan, MBBS, 9/F, Division of Cardiology, Department of Medicine and Therapeutics, Clinical Sciences Building, Prince of Wales
Hospital, Shatin, NT, Hong Kong SAR, China. E-mail: bryan.yan@cuhk.edu.hk
Received January 10, 2018; accepted March 14, 2018.
ª 2018 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley. This is an open access article under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is
non-commercial and no modifications or adaptations are made.
DOI: 10.1161/JAHA.118.008585
Journal of the American Heart Association
1
Contact-Free Screening of Atrial Fibrillation
Yan et al
What Is New?
• It is feasible to accurately detect atrial fibrillation without
physical contact by analyzing photoplethysmographic signals from a person’s face using a smartphone camera.
What Are the Clinical Implications?
• The convenience of a contact-free approach to detect atrial
fibrillation is attractive for community screening and has the
potential to be useful for screening over a distance using
telemedicine.
Downloaded from http://ahajournals.org by on September 28, 2023
a systematic review, single time-point screening of a general
population aged >65 years detected new AF in 1.4%.7 Current
guidelines recommend opportunistic screening by pulse palpation, followed by confirmatory 12-lead ECG or single-lead
ECG rhythm strip in patients >65 years of age.8,9 Limitations of
screening by pulse palpation include variable diagnostic
accuracy10 and the time to perform a 12-lead ECG.
In recent years, several handheld devices, including standalone and smartphone-based devices and applications, have
been developed for point-of-care AF screening.11,12 The
AliveCor heart monitor (AliveCor, San Francisco, CA) is a Food
and Drug Administration–approved handheld single-lead ECG
device attached to a smartphone with an AF detection
application. Initial validation study of the AliveCor for AF
detection has shown high sensitivity of 98% and specificity of
97%.13 However, the diagnostic performance of the AliveCor as
a screening test in a “real-world” primary care setting was lower,
with sensitivity of 98% (95% confidence interval [CI], 92%–100%)
and specificity of 91% (95% CI, 89%–93%) in the SEARCH-AF
(Screening Education And Recognition in Community pHarmacies of Atrial Fibrillation) study using the same algorithm.12
In addition to handheld ECG devices, smartphones are
capable of detecting pulsatile photoplethysmographic signals
related to cardiac-induced fluctuations in tissue blood
volume using the built-in cameras and LED (light-emitting
diode) smartphone flash.14,15 To date, the photoplethysmographic signal is typically recorded by placing a finger over
the smartphone camera lens, which measures changes in
reflected light intensity from the LED caused by blood
volume changes in the fingertip. Recent studies have
demonstrated both the Cardiio Rhythm and PulseSMART
finger photoplethysmographic-based smartphone applications have high sensitivity (92.7% and 97.0%, respectively)
and specificity (99.7% and 93.5%, respectively) in discriminating an irregular pulse during AF from sinus rhythm.16,17
Facial video recording using the smartphone camera is
a novel method of detecting a pulsatile facial photoplethysmographic signal without physical contact,18–20 with
DOI: 10.1161/JAHA.118.008585
the potential for distant screening. A small proof-of-concept
study supported the feasibility of such a contact-free method
for AF detection,19 but the performance of facial photoplethysmography for the detection of AF in a prospective study has not
been reported. The primary aim of this study was to evaluate
the performance of a smartphone application, Cardiio Rhythm,
in detecting AF from facial photoplethysmographic signals
acquired without physical contact, with the patient using 12lead ECG as the reference standard. In addition, we compared
the AF detection performance of facial photoplethysmography
with fingertip photoplethysmography, the typical method for
acquiring photoplethysmographic signals using a smartphone.
Methods
The data, analytic methods, and study materials will not be
made available to other researchers for purposes of reproducing the results or replicating the procedure.
Study Population
Inpatients at the Prince of Wales Hospital cardiology ward were
recruited between 1 April and 30 November 2016. These
patients were admitted for clinical reasons. The in-hospital
environment provided a controlled setting and made it more
feasible to perform reference 12-lead ECG measurements.
Informed consent was obtained from all patients, and the study
was approved by the local institutional review board, Joint
Chinese University of Hong Kong–New Territories East Cluster
Clinical Research Ethics Committee (reference no. 2016.550).
Clinical characteristics were recorded, including age, sex,
and history of heart failure, hypertension, stroke, and
coronary artery disease. Stroke prevention therapy, including
oral anticoagulants, antiplatelet therapy, and left atrial
appendage occlusion, was recorded. CHA2DS2-VASc score
(congestive heart failure, hypertension, age, diabetes mellitus,
previous stroke/transient ischemic attack, female sex, and
vascular disease) was calculated on the basis of clinical data.
Body height and weight were measured under standard
anthropometry procedures, and body mass index was calculated as weight (in kilograms) divided by height (in square
meters). Blood pressure measurements were taken using an
automatic blood pressure monitor (Tango M2; SunTech
Medical, Inc, NC) before AF measurements. The facial skin
color of participants was evaluated using the von Luschan
skin color chart (range, 1–36, with 1 being a lightest skin
color and 36 being a darkest skin color; Figure S1).21
Study Setup for AF Measurement
Two iPhone 6S units (Apple Inc, Cupertino, CA) installed with
the Cardiio Rhythm application (beta version; Cardiio, Inc,
Journal of the American Heart Association
2
ORIGINAL RESEARCH
Clinical Perspective
Contact-Free Screening of Atrial Fibrillation
Yan et al
Cardiio Rhythm Smartphone Application
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Cardiio Rhythm application is a novel smartphone application
that measures the rhythm of the heart through recording
pulsatile photoplethysmographic signal from either the fingertip or the face without physical contact. The camera detects
subtle beat-to-beat variations of skin color on the basis of the
amount of reflected light that changes, according to the arterial
blood volume pulsations. Photoplethysmographic waveforms
were sampled at 30 Hz, and each measurement recorded 512
samples (17 seconds). Photoplethysmographic waveforms
were filtered by using a bandpass filter (0.7–4.0 Hz) to remove
baseline wander and high-frequency noise. Detection of AF was
based on an irregularly irregular pattern in the photoplethysmographic waveform attributable to AF. Briefly, the algorithm
computed repeating patterns in the photoplethysmographic
waveform on the basis of autocorrelation analysis and classified the patterns using a previously trained support vector
machine.22 Each photoplethysmographic recording was
encrypted and wirelessly transmitted to a secure cloud server
to compute the likelihood of a “regular” or an “irregular” pulse,
expressed as a percentage (100% being the highest likelihood)
(Figure 1A and 1B). When the Cardiio Rhythm application was
unable to interpret the photoplethysmographic signal, the
reading was defined as “uninterpretable”. Three consecutive
uninterpretable photoplethysmographic readings are rare with
normal sinus rhythm and can be attributable to variability in
photoplethysmographic wavelength and amplitude during AF,
leading to uninterpretable photoplethysmographic signals. In
this study, a positive test screening for AF was defined as either
of the following: (1) detection of an irregular heart rhythm in ≥1
photoplethysmographic measurements or (2) 3 consecutive
uninterpretable photoplethysmographic measurements. All
other combinations were categorized as a negative test
screening for AF.
The Cardiio Rhythm application uses the same heart rate
measurement algorithm as the Cardiio: Heart Rate Monitor
application that has previously been validated for measuring
heart rate at rest and after exercise against 12-lead ECG23
and against a Food and Drug Administration–cleared pulse
oximeter.24
Facial Photoplethysmographic Detection
Each participant was asked to sit in front of an iPhone placed
upright on a desk 30 cm away. A large circle that displayed
the front camera’s field of view appeared on the iPhone
screen once the Cardiio Rhythm application was activated and
the participant was instructed to position his/her entire face
Figure 1. Examples of photoplethysmographic (PPG) recordings analyzed by Cardiio Rhythm application from patients in atrial fibrillation (A)
and sinus rhythm (B). C, Setup to acquire PPG signals from face by using the front camera. D, Obtaining PPG signals from fingertip by using the
back camera.
DOI: 10.1161/JAHA.118.008585
Journal of the American Heart Association
3
ORIGINAL RESEARCH
Cambridge, MA) were used for simultaneous facial and
fingertip photoplethysmographic detection. A 12-lead ECG
(Mortara ELI 150c; Milwaukee, WI) was performed
after photoplethysmographic measurements. The background light intensity was measured in unit of lux during
signal acquisition.
Contact-Free Screening of Atrial Fibrillation
Yan et al
Fingertip Photoplethysmographic Detection
The finger photoplethysmographic signal was measured
simultaneously with the facial photoplethysmographic measurement. Patients were instructed to cover the camera on
the back of a second iPhone with their left index finger
(Figure 1D). Continuous pulsatile photoplethysmographic signal from the fingertip detected by the camera was displayed in
real time on the bottom of the iPhone screen. Again, 3
consecutive 20-second (total of 60 seconds) measurements
were performed for each patient.
ECG (12 Lead)
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A 12-lead ECG was performed immediately after facial and
finger photoplethysmographic measurements to serve as the
reference standard. The ECG recordings were analyzed for the
presence of AF by a cardiologist (B.P.Y.) blinded to the
photoplethysmographic results. Patients with an implanted
pacemaker were excluded if the pacemaker was configured in
active pacing mode.
Statistical Analysis
Continuous and discrete variables were presented as
meansSD or median (interquartile range) and as numbers
and percentages, respectively. Independent t test and MannWhitney U tests were performed to test the difference
between means and medians, respectively. v2 Test and
Fisher’s exact test were performed to determine differences
in categorical variables between groups. The diagnostic
accuracy of both facial and finger photoplethysmography for
AF detection was determined using 12-lead ECG as the
reference standard. The calculations of sensitivity, specificity, predictive value, likelihood ratio, diagnostic odds ratio,
and prevalence for AF diagnosis were performed by using
292 contingency tables as simple proportions, with corresponding 95% CIs. Cohen’s j coefficients were calculated to
measure the agreement between finger and facial photoplethysmographic detection for AF. A j value of >0.8
indicated excellent agreement.25 Univariate logistic regression models were performed to explore differences between
DOI: 10.1161/JAHA.118.008585
characteristics of participants and facial photoplethysmographic detection failure. Multivariate logistic regression
analysis was then performed to determine predictors of
facial photoplethysmographic detection failure, controlling
for age, sex, facial skin color, background light intensity,
stroke risk scores, antithrombotic treatment received, systolic blood pressure, and resting heart rate. Last, a backward
stepwise multivariate logistic analysis was used. All analyses
were 2 tailed, and P
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