Table 1

Features, caveats and pitfalls of main indices used in SLE: the SLEDAI-2K, the SELENA-SLEDAI Flare Index and the SLICC/ACR Damage Index

Index	Features and clinical relevance	How to use, caveats and pitfalls
SLEDAI-2K	Features Scores the activity of 24 clinical presentations within a period of 28 days Organ involvement is weighted from 1 to 8 (range 0–105) Grading of severity SLEDAI=0 Remission SLEDAI=1–4 Low activity SLEDAI=5–10 Moderate activity SLEDAI >10 High activity Clinically important changes Increase >3 = Flare Decrease <3 = Improvement Change ±3 = Persistent activity	Combine SLEDAI with a Physician Global Assessment (PGA) (graded from 0 to 3 on a 10 cm long straight line) Assess PGA before calculating the SLEDAI, to avoid bias in physician assessment Score items only if confidently attributed to lupus Pitfalls: pyuria due to UTI or asymptomatic bacteriuria; hair loss or leucopenia due to drug side effect; stroke due to atherosclerosis; other neuropsychiatric manifestations due to metabolic abnormalities, drug side effects or CNS infections Score items only if they are reversible Pitfalls: scarring alopecia; ‘fixed’ lupus rash with scar; ‘fixed proteinuria’ Time needed to complete: 5–10 min
SELENA-SLEDAI Flare index	Flares defined by: changes in SLEDAI score and/or individual manifestations and/or changes in treatment and/or need for hospitalisation and/or changes in PGA Mild/moderate flare Change in SELENA-SLEDAI instrument score of 3 points or more (but not to >12) Increase in prednisone, but not to >0.5 mg/kg/day Addition of NSAID, hydroxychloroquine for SLE activity ≥ 1.0 increase in PGA score, but not to >2.5 Severe flare Change in SELENA-SLEDAI instrument score to >12 points Increase in prednisone to >0.5 mg/kg/day New cyclophosphamide, azathioprine, methotrexate, MMF or biologics for SLE activity Hospitalisation for SLE Increase in PGA score to >2.5	Patients classify for flare if ≥1 criterion for flare is present Treatment changes qualify for a flare, even in case of persistent activity rather than exacerbation A treatment change does not always correlate with physician assessment of disease activity A ‘major flare’ can result from small increases in disease activity from different domains No discrimination between mild vs moderate flares Both number and severity of flares have been associated with irreversible damage accrual (SDI increase) Time needed to complete: 10–20 min
SLICC/ACR DAMAGE INDEX (SDI)	Features Scores irreversible damage accrual in 12 organ systems Damage due to either disease or medication side-effects (eg, glucocorticoids or cyclophosphamide) Grading of damage SDI 0 No damage SDI≥1 Irreversible damage present SDI≥3 Severe damage present Clinical relevance Any increment in the SDI is prognostically significant, associated with further damage accrual and mortality	Score damage occurring only after SLE onset Score items present for at least 6 months (beware for potentially reversible manifestations, eg, proteinuria, alopecia) Since damage items are irreversible, SDI can only increase over time (unlike eg, the Health Assessment Questionnaire in RA) Individual items get same score if present, irrespective of extent of damage and impact on patient’s life Examples: Stroke with minimal neurologic sequelae vs severe neurologic deficit; pulmonary fibrosis limited vs extensive Time needed to complete: 10–20 min

ACR, American College of Rheumatology; CNS, central nervous system; MMF, mycophenolate mofetil; NSAID, non-steroidal anti-inflammatory drugs; RA, rheumatoid arthritis; SDI, SLICC/ACR Damage Index; SELENA, Safety of Estrogens in Lupus Erythematosus National Assessment; SLE, systemic lupus erythematosus ; SLEDAI, SLE Disease Activity Index; SLICC, Systemic Lupus International Collaborating Clinics; UTI, urinary tract infection.