surveillance of peripheral arterial disease cases …...right lower extremity critical limb...

©2017 MFMER | slide-1

Surveillance of Peripheral Arterial

Disease Cases Using Natural Language Processing of Clinical

Notes Naveed Afzal, Sunghwan Sohn, Christopher G. Scott, Hongfang Liu, Iftikhar J. Kullo, Adelaide M. Arruda-Olson


Peripheral arterial disease (PAD)

• Affects 8.5 million in US, 200 million worldwide • Associated with high risk of mortality and morbidity • Under-diagnosed and undertreated • Lack of awareness of PAD-associated risks for

adverse cardiovascular outcomes • Diagnosed by ankle-brachial index (ABI) test but this

method remains underutilized

Kullo & Rooke: NEJM, 2016; Hirsch et al: JAMA, 2001; Gerhard-Herman et al: J Am Coll Cardiol, 2016


Background

• Manual methods for disease surveillance are costly, time-consuming and inconsistent

• Automated surveillance of clinical notes from EHRs may effectively identify PAD cases

• Use NLP to extract PAD related information from narrative clinical notes


Objectives • To develop and validate a PAD surveillance

system using NLP for detection of PAD symptoms from narrative clinical notes


PAD diagnosis based on ABI test

•  Reports were in PDF format and were not part of clinical notes

•  PAD cases •  ABI ≤ 0.90 rest or post-

exercise •  ≥20% decrease ABI after

exercise •  High ABI >1.40 = poorly

compressible arteries

•  Controls •  Normal ABI results

•  Date of ABI testing = index date

Kullo & Rooke: NEJM, 2016


Concept features and rules

Documents, patient IDS, dates

NLP Algorithm

System output

EHR System

Sentence Detection

Tokenization

Concept Identification

Assertion

Patient Classification

Evaluation

ABI (Gold

Standard)


PAD-NLP Algorithm • Expert clinician manually reviewed clinical notes

•  20 patients with PAD •  20 patients without PAD

• Created list of PAD-related keywords for NLP algorithm prototype

• List of keywords refined by manual review of charts by a board certified cardiologist

Afzal et al: J Vasc Surg, 2017


Examples of keywords for confirmation of PAD Right lower extremity critical limb ischemia. She has history of peripheral vascular disease

She has been followed in the Wound Care Center this year for ulcerations to the toes of her right foot

Ultrasound shows severe right lower extremity atherosclerotic disease, beginning at the level of the right common femoral artery Noninvasive lower extremity arterial study demonstrated indeterminate ankle-brachial indices due to poorly compressible vessels bilaterally His past medical history is also significant for peripheral arterial occlusive disease with aorto-bifemoral bypass, Peripheral vascular disease Critical limb ischemia right lower extremity LLE ischemia Noncritical infrapopliteal level lower extremity arterial occlusive disease bilaterally Lower extremity atherosclerosis obliterans Severe lower extremity arterial occlusive disease

Examples of keywords for exclusion of PAD There is no evidence of critical limb ischemia No evidence of PAD Vascular lab - normal lower extremity arterial study No evidence of arterial occlusive disease


Keywords - NLP algorithm Confirmation - Disease Location

lower extremities/extremity; lower limbs/limb; Leg /legs; Iliac/femoral/tibial/popliteal artery/ arteries; Distal/ infrarenal /abdominal aorta/aorto (bi)iliac/ aorto (bi)iliac/aorto(bi)-iliac; aorto-(bi)femoral; foot, toe, toes, shin; plantar, heel, ankle, interdigital; below/above knee, Claudication /calf pain; Ischemic ulcer/ulcers; ASO/Arteriosclerosis obliterans/ arterial sclerosis obliterans/ atherosclerotic disease; PAD/ Peripheral arterial disease/Peripheral vascular disease /Peripheral arterial occlusive disease

Confirmation - Diagnosis Arterial occlusive disease/occlusion/occluded; Stenosis; non compressible vessels (NCV), non-compressible arteries (NCA), poorly compressible vessels (PCV), stiff vessels/ arteries ischemia; positive ABI/ankle brachial index/ vascular labs/ extremities study /arterial studies; revascularization/recanalization/bypass/angioplasty/PTA/stenting/stent/graft/endarterectomy/ endarterectomies; thrombectomy/thrombosis/thromboembolectomy/embolectomy/ embolectomies

Exclusion Family history of, Upper extremities/Upper extremity; Arm/arms, hand(s); Brachial artery, axillary artery, radial artery, ulnar artery; carotid, innominate artery, subclavian artery; mesenteric artery; celiac artery; AAA, abdominal aortic aneurysm/abd aortic aneurysm; renal arteries/artery; coronaries, coronary arteries/ artery /cerebrovascular-disease /arteries/artery; Amputation; traumatic/trauma; sarcoma/osteoma; pseudoclaudication/pseudoclaudicatory pain; diabetic foot, hammer toe/ toes; vascular calcification; varicose veins


PAD-NLP Algorithm Rules

PAD One disease location keyword + one diagnostic

keyword within two sentences

Non-PAD 1) No PAD criteria 2) One exclusion keyword


Note Types Note Sections Service Groups Consult Impression / Report / Plan Primary Care

Subsequent Visit Diagnosis Hospital Internal Medicine

Patient Progress Principal/primary Diagnosis General Medicine

Supervisory Secondary Diagnoses Family Medicine

Limited Exam Past Medical/Surgical History Critical Care

Specialty Evaluation Ongoing Care Urgent Care

Multisystem Evaluation Immunizations Cardiology

Injection Key Findings / Test Results Vascular

Educational Visit Pre-Procedure Information Pulmonary

Hospital Service Transfer Post-Procedure Information Oncology

Vital Signs Nephrology

Current Medications Neurology

Revision History Pathology

Special Instructions Gastroenterology

Advance Directives Vascular Wound Care

Discharge Activity Vascular Surgery

Final Pathology Diagnosis Cardiac Surgery

Included


Note Types Note Sections Service Groups Miscellaneous Chief Complaint Orthopedic

Test- Oriented Miscellaneous History of Present Illness Podiatry Dismissal Summary Family History Endocrinology Therapy System Reviews Emergency Medicine Emergency Medicine Hospital Admission Note Visit

Anticipated Problems and Interventions

Allergy

Hospital Admission Note Informed Consent Dermatology Emergency Medicine Visit Patient Education Sports Medicine

Physical Examination Spine Center Work Rehabilitation Plastic Surgery

Nursing Home Social Services Addiction

Excluded

Afzal et al: J Vasc Surg, 2017


REP PAD Cohort • 1569 patients

•  806 cases •  763 controls

• Average age: 71 years • 44% women • 90% white

2000 2005

ABI test date 21-day

2015 2017 2010


Performance of PAD-NLP algorithm vs. gold standard (ABI)

PPV 0.93

Sensitivity 0.70

NPV 0.80

Specificity 0.95


Temporality of PAD-NLP Algorithm • Compared temporal association between PAD-

NLP algorithm inception date (date on which NLP algorithm classified patient as PAD) with gold standard index date for each PAD patient

• For true positive cases, difference between NLP algorithm inception date and gold standard index date was measured in days


Temporality of PAD-NLP Algorithm

Before gold standard index date 329 cases (41%)

At gold standard index date 93 cases (12%)

After gold standard index date but within 21 day-window

141 cases (18%)


Temporality of PAD-NLP Algorithm

0

20

40

60

80

100

120

140

160

180

<-3000 -2999 to -2000

-1999 to -1000

-999 to -500 -499 to -100 -99 to -1 0 1 to 20

Number of patients

true positives

Number of days from ABI test


Discussion • PAD-NLP algorithm identified PAD cases from

clinical notes with high PPV • Prior to ABI test date in 41% of the cases from the

community • Delay in establishing PAD diagnosis despite

presence of PAD symptoms


Study Limitations • Data were retrieved from a single

academic medical center • Results may not be generalized to other

practice settings


Clinical Implications • Accurate and timely detection of actual or possible

PAD will: • Remind clinicians to order ABI testing confirming

diagnosis of PAD •  Implement risk modification strategies in PAD

patients • PAD-NLP algorithm may be incorporated to clinical

CDS to identify PAD patients • Future studies will evaluate impact of CDS system on

outcomes in PAD patients


Conclusions • PAD-NLP surveillance algorithm enabled

early identification of PAD with high PPV • This may promote diagnosis earlier in the

course of PAD


Acknowledgements

• Grants • NHLBI: K01HL124045 • NHGRI: HG04599 and HG006379 • NIA: R01AG034676 • NIGMS: R01GM102283A1


Questions ?

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