Table 1.

Phase I/II Item Generation and Item Reduction Surveys During New Antiphospholipid Syndrome Classification Criteria Development

	Survey Question and Response Option	Goal	Response Rate	Respondents	Results Summarized	Final Number of Candidate Criteria
Phase I
Question #1	Question: ‘Describe all features (historical, clinical, laboratory, radiological, and pathological) that in your experience can occur as part of aPL/APS spectrum” Response Option: Open-Ended	Identify potential candidate criteria with “positive weight”	41/54 (76%)	Of 41, 18 were rheumatologists, 5 hematologists, 5 clinical immunologists, 5 nephrologists/cardiologists/neurologists, 4 internists, 2 pediatric rheumatologists, and 2 obstetricians.	Distribution of Potential aPL/APS Spectrum Candidate Criteria by system (#):  • Neurologic (25)  • Laboratory (aPL) (23)  • Obstetric (16)  • Dermatologic (15)  • Renal (12)  • Vascular (10)  • Cardiac (9)  • Laboratory (non-aPL) (9)  • Other (7)  • Hematology (5)  • Pulmonary (5)  • Gastrointestinal (4)  • Musculoskeletal (4)  • Endocrinologic (3)  • Ophthalmology (2)  • Auditory (2)  • Family History (1)	• 152 items (based on question 1) expanded to 261 to include negatively weighted criteria and subgroups  • Of note, some items were reported as both positive and negative candidate criteria; we included those items in the expanded list.
Question #2	Question: ‘Describe all features (historical, clinical, laboratory, radiological, and pathological) or concomitant diseases that, if present, would make you question the diagnosis of APS even if aPL tests are positive’ Response Option: Open-Ended	Identify potential candidate criteria with “negative weight”			Distribution of Potential Negative Weight Criteria (categories):  • Laboratory (aPL vs. non-aPL)  • Other Thrombosis Risk Factors  • Infections  • Traditional CVD Risk Factors  • Autoimmune Diseases  • Malignancy  • Neurological  • Histological  • Elderly  • Thrombotic Microangiopathies  • Radiological  • Medications  • Lupus Manifestations  • Strong Family History  • Bleeding  • Other
Question #3	Question: ‘When you consider the diagnosis of APS, do you think of APS patients in different subpopulations? If so, please describe how you categorize these patients.” Response Option: Open-Ended	Categorize candidate criteria			Subpopulations of APS patients categorized by:  • Age  • Clinical Manifestations  • aPL Profile  • Risk Level
Phase II
Survey A	Question: “Consider two patients who are exactly the same except that one has the clinical feature presented and the other does not. Please rate each feature in terms of how strong this feature is in differentiating APS from other similar conditions, i.e., specific for APS” using a Likert scale (−5 to +5). Response Option: Please rate each item based on a scale of −5 to +5, with +5 being “extremely specific" for APS.	Item Reduction by elimination of low specificity items and organizing higher specificity items into separate domains	43/61 (71%)	• Of 43, 22 were rheumatologists, 4 hematologists, 4 nephrologists/cardiologists/neurologists/vascular specialists, 4 internists, 3 clinical immunologists, 3 pediatric rheumatologists, 2 pediatric hematologists, and 1 obstetrician.	• See Table 2	132 items (reduced to 64 items and 10 domains when overlapping items were eliminated)
Survey B	“Consider two patients who are exactly the same except that one has the clinical feature presented and the other does not. Please rate each feature in terms of how strong this feature is in differentiating APS from other similar conditions, i.e., specific for APS” using a Likert scale (−5 to +5). Response Option: Please rate each item based on a scale of −5 to +5, with +5 being “extremely specific" for APS.	Further item reduction to goal of approximately 30 candidate criteria	19/19 (100%)	Of 19, 8 were rheumatologists (adult), 2 hematologist, 2 cardiologists/vascular medicine specialists, 2 immunologists, 2 obstetrician, 1 pediatric rheumatologist, 1 neurologist, and 1 classification criteria methodologist	• See Table 3	• 27 items and 6 domains