Connective tissue diseases Original research Obstetrical outcome and treatments in seronegative primary APS: data from European retrospective study Noemie Abisror,1 Yann Nguyen ,2 Luca Marozio,3 Enrique Esteve Valverde,4 Sebastian Udry,5 Daniel Enrique Pleguezuelo,6 Paul Billoir,7 Karoline Mayer-Pickel,8 Geoffrey Urbanski,9 Polona Zigon,10 Claire De Moreuil,11,12 Ariela Hoxha,13 Holy Bezanahary,14 Lionel Carbillon ,15,16 Gilles Kayem,17,18 Marie Bornes,19 Cecile Yelnik,20 Cathererine Johanet,21 Pascale Nicaise-Roland,22 Marc Lambert,20 Valéry Salle,23 Omar Jose Latino,5 Eric Hachulla ,20 Chiara Benedetto,3 Marie Charlotte Bourrienne,24,25 Ygal Benhamou,7 Jaume Alijotas-Reig,26,27 Olivier Fain,1 Arsène Mekinian ,1 On behalf of European Forum on Antiphospholipid Antibodies To cite: Abisror N, Nguyen Y, ABSTRACT Marozio L, et al. Obstetrical Objective To compare characteristics, pregnancies and Key messages outcome and treatments treatments during pregnancies of seronegative and in seronegative primary APS: What is already known about this subject? data from European seropositive antiphospholipidsyndrome (APS), to analyse factors associated with obstetrical outcome. ► Several studies reported about seronegative APS retrospective study. RMD Open Patients and methods Inclusion criteria were: (1) mainly defined by clinical criteria and among them 2020;6:e001340. doi:10.1136/ thrombotic and/or obstetrical APS (Sydney criteria); (2) the series with clinical criteria and at least one rmdopen-2020-001340 absence of conventional antiphospholipid antibodies (APL); positive non-criteria APL are lacking. ► Supplemental material is (3) at least one persistent non-conventional APL among IgA What does this study add? published online only. To view please visit the journal online anticardiolipin antibodies, IgA anti-B2GPI, anti-vimentin G/ ► Several non-criteria APL can be detected in patients (http://dx.doi.org/10.1136/rmdo M, anti-annexin V G/M, anti-phosphatidylethanolamine G/M with clinical features consistent with APS without any pen-2020-001340). and anti-phosphatidylserine/prothrombin G/M antibodies. conventional APL, with various prevalent rates. The exclusion criteria were: (1) systemic lupus Received 28 May 2020 Revised 27 June 2020 erythematosus ( SLE) or SLE-like disease; and (2) other How might this impact on clinical practice? Accepted 23 July 2020 connective tissue disease. ► The detection of non-criteria APL and thus the Results A total of 187 women (mean 33±5 years) with diagnosis of seronegative APS could discuss the seronegative APS were included from 14 centres in Austria, therapeutic management similar to seropositive Spain, Italy, Slovenia and France and compared with 285 APS, but well-designed controlled studies are patients with seropositive APS. Seronegative APS has more necessary. obstetrical rather than thrombotic phenotypes, with only 6% of venous thrombosis in comparison to seropositive APS. Cumulative incidence of adverse obstetrical events was similar in seronegative and seropositive APS patients, INTRODUCTION although higher rates of intrauterine deaths (15% vs 5%; Antiphospholipid syndrome (APS) is an auto- p=0.03), of preeclampsia (7% vs 16%, p=0.048) and lower immune disease characterised by vascular live birth term (36±3 vs 38±3 weeks of gestation; p=0.04) thrombosis, various obstetrical adverse events were noted in seropositive APS. The cumulative incidence of and persistent antiphospholipid antibodies adverse obstetrical events was significantly improved in (APL). The conventional APL includes lupus © Author(s) (or their treated versus untreated seronegative APS (log rank<0.05), anticoagulant (LA), IgG/M anticardiolipin employer(s)) 2020. Re-use permitted under CC BY-NC. No whereas there was no difference between patients who antibodies (aCL) and IgG/M antibodies commercial re-use. See rights received aspirin or aspirin-low-molecular weightedheparin against β2GPI (anti-β2GPI) antibodies.1 Sero- and permissions. Published combination. negative APS has been recently defined in by BMJ. Conclusion Several non-criteria APL can be detected in patients with obstetrical and thrombotic clini- patients with clinical APS features without any conventional For numbered affiliations see cal APS features (Sydney criteria), but without APL, with various rates. The detection of non-criteria APL end of article. detectable conventional APL.2 In seronegative and thus the diagnosis of seronegative APS could discuss Correspondence to APS, the possibility of persistent non-criteria the therapeutic management similar to seropositive APS, Arsène Mekinian; but well-designed controlled studies are necessary. APL has been raised. Several non-criteria anti- arsene.mekinian@aphp.fr phospholipid antibodies, such as IgA aCL and Abisror N, et al. RMD Open 2020;6:e001340. doi:10.1136/rmdopen-2020-001340 1 RMD Open anti-β2GPI, anti-phosphatidylethanolamine (anti-PE), miscarriage (<10 weeks of gestation), fetal loss (≥10 weeks anti-phosphatidylserine/prothrombin (anti-PS/PT), anti- of gestation), intra-uterine growth restriction (IUGR), pre- vimentin and anti-annexin V and II antibodies can actually maturity (<34 weeks of gestation), pre-eclampsia or be tested.3–6 However, there is a paucity of studies evaluat- eclampsia, hemolysis, elevated liver enzymes and low plate- ing the link between these autoantibodies and clinical let count (HELLP) syndrome, placental abruption, gesta- status, in particular for obstetrical outcomes.7 Studies tional arterial hypertension and arterial and/or venous mostly evaluated the prevalence of these persistent non- thrombosis during the pregnancy. All these data were criteria APL in thrombotic clinical subsets, showing included in standardised electronic files which were filled 10–15% of prevalent among patients with unexplained by the practitioner of each patient. venous thrombosis. Accurate identification of patients Non-criteria APL testing included anti-β2GPI IgA, anti- with APS is essential, as treatment during pregnancy sig- annexin V antibodies, anti-PE IgG and IgM antibodies, nificantly improves the fetal and maternal outcomes.8 Stu- anti-PS/PT IgG and IgM antibodies, IgA aCL or anti- dies reporting pregnancy outcomes in seronegative vimentin antibodies. For patients with at least one positive clinical APS with presence of non-criteria APL, treatments non-criteria APL, non-criteria APL positivity was con- and comparison of this condition to seropositive APS are firmed to be persistent at 12 weeks. Because of non- still lacking. From this retrospective European study we standardisd tests for seronegative APL, APL were aimed to (1) describe the clinical and laboratory features expressed as positives or negatives at 99° percentiles, with- of seronegative clinical APS with detectable persistent non- out considering the titers. criteria APL; (2) describe the fetal, maternal outcomes The control group was selected among women with and the treatments during pregnancies; (3) compare ser- primary seropositive APS (Sydney criteria), included in onegative APS to seropositive APS women and (4) analyse the French APS and Lupus Registry. This registry retro- factors associated with adverse obstetrical outcomes in spectively included APS patients, mainly in two referral seronegative and seropositive APS. centres (Cochin and Lille hospitals). The exclusion cri- teria were the same as for the seronegative APS: (1) associated SLE or SLE-like disease (SLE features and/or PATIENTS AND METHODS positive antinuclear autoantibodies) and (2) other sys- Patients’ selection temic connective tissue disease (Sjogren’s syndrome, sys- A retrospective study was initiated with the European temic sclerosis, myositis, etc.). For the first analysis Forum on Antiphospholipid Antibodies from 2017 to comparing phenotypes among seropositive and serone- 2019 and all practitioners were asked to fill gative APS patients, we selected all APS women included a standardised excel form. in the registry, including obstetrical and thrombotic APS Inclusion criteria were: (1) arterial and/or venous phenotypes and excluding SLE-associated APS. For the thrombotic; and/or obstetrical primary clinical APS (Syd- comparison of subsequent pregnancies following APS ney criteria) (not explained by usual causes, p.e. chromo- diagnosis, we only selected women with seropositive APS somal, uterine, hormonal, etc., abnormalities for (obstetrical and/or thrombotic phenotype), who had at recurrent miscarriages); (2) absence of conventional least one registered pregnancy after the APS diagnosis antiphospholipid antibodies; (3) presence of at least similarly to the seronegative APS women. one persistent non-conventional APL among IgA aCL, IgA anti-β2GPI, anti-vimentin G/M, anti-annexin V G/ Statistical analysis M, anti-PE G/M, anti-PS/PT G/M antibodies and (4) at Descriptive analyses were expressed as proportions (%) least one pregnancy after the diagnosis of seronegative for categorical variables and means (SD) for continuous APS. The clinical APS criteria for thrombosis were other- variables. First, we compared phenotypes from all serone- wise unexplained thrombosis and for obstetrical events gative and seropositive APS patients, using t-tests for con- recurrent unexplained early miscarriages, unexplained tinuous variables and Chi-squared tests for categorical intrauterine deaths and/or preeclampsia and prematur- variables. Then, we compared the pregnancy outcomes ity from placental insufficiency otherwise unexplained. occurring after APS diagnosis. To study obstetrical out- The exclusion criteria were: (1) associated systemic comes, we chose the following outcomes: fetal loss lupus erythematosus (SLE) or SLE-like disease (SLE fea- <10 weeks, fetal loss ≥10 weeks, premature birth tures and/or positive antinuclear autoantibodies) and <34 weeks of gestation, maternal complications (HELLP (2) other systemic connective tissue disease (Sjogren’s and/or preeclampsia, thrombosis) and the presence of syndrome, systemic sclerosis, myositis, etc.). any of these events. To assess the association between APL Maternal age, characteristics of previous thrombosis and status and obstetrical outcomes, univariate analyses were obstetrical features, associated thrombotic and cardiovas- performed using t-tests for continuous variables, and chi- cular factors (obesity, hypercholesterolaemia, tobacco use, squared tests for categorical variables. We subsequently diabetes mellitus, arterial hypertension, constitutional used multivariate models using logistic regressions, with thrombophilia), course and outcome of previous pregnan- all variables associated with the outcome (p<0.2) in uni- cies and treatments during the pregnancies were variate analyses. In those analyses, missing variables were recorded. Adverse pregnancy outcomes included early imputed using multiple imputations. Kaplan–Meier 2 Abisror N, et al. RMD Open 2020;6:e001340. doi:10.1136/rmdopen-2020-001340 Connective tissue diseases curves and log-rank tests were used to compare the cumu- (n=0/65) (online supplemental table 1). A single non- lative incidence of adverse obstetrical events first accord- criteria APL was noted in 131 women (70%), with double ing to the treatment among seronegative APS, then and triple positivity’s in 50 (27%) and 6 cases (3%), comparing seronegative and seropositive APS. All ana- respectively. Single-triple and double-triple positive sero- lyses were performed using R software, version 3.4.2 (R negative APS have similar age and frequencies of obste- Foundation for Statistical Computing, Vienna, Austria). trical ad thrombotic APS features (data not shown). Comparing pregnancy outcomes of seronegative APS, women with double-positive non-criteria APL had signifi- RESULTS cantly more frequent fetal loss than single-positive APS A total of 187 women (mean age 33±5 years) with serone- (13/28 (46%) vs 16/70 (23%); p=0.03) despite the use of gative APS were included from 14 centres in Austria, similar frequencies of aspirin, low-molecular weighted Spain, Italy, Slovenia and France and compared with heparin (LMWH) and additional therapies during the 285 patients with seropositive APS (table 1). Seronegative pregnancies. APS had mostly obstetrical phenotypes rather than The cumulative incidence of adverse obstetrical events venous thrombosis, with only 6% having experienced was significantly improved in treated seronegative APS a venous thrombosis. Non-criteria APL in seronegative versus untreated ones (log rank <0.05), whereas there APS were anti-β2GPI IgA antibodies (n=3/127), anti- was no difference between patients who received aspirin annexin V antibodies (n=43/185), anti-PE IgG (n=19/ or aspirin-LMWH combination (figure 1). The rates of 124) and IgM antibodies (n=43/124), anti-PS/PT IgG live-birth pregnancies treated with aspirin-LMWH combi- (n=66/186) and IgM antibodies (n=69/186), without nation were significantly higher than pregnancies result- any IgA aCL (n=0/53) or anti-vimentin antibodies ing in fetal loss (46/75 (61%) vs 16/43 (37%), p=0.002). Women with isolated recurrent miscarriages treated by aspirin and LMWH combination (n=48 pregnancies; Table 1 Characteristics of seronegative and seropositive 89%) have live birth pregnancies in 31 (57%), whereas APS women those with prematurity related to placental insufficiency Seronegative Seropositive under aspirin and LMWH in 9 (45%) have live birth APS (n=187) APS (n=285) pregnancies in 18 (82%). General characteristics The control group of seropositive APS included 285 women with a mean age of 36±5 years. The APL were Caucasian (n; %) 150 (82) 188 (66) the LA (n=211; 74%), aCL (n=228; 80%) and anti- Age (years) 33±5 36±5† β2GPI antibodies (183 cases; 64%), with triple positivity Obesity (n; %) 15 (9) 32 (11) Arterial hypertension 3 (2) 54 (19)† (n; %) Diabetes mellitus (n; %) 1 (1) 18 (6)† Tobacco use (n; %) 12 (7) 33 (12)† Hypercholesterolaemia 0 69 (24)† (n; %) Protein S deficiency/V 0/1 (1) 8 (3)/10 (4)† Leiden (n; %) APS features Thrombotic APS Arterial APS (n; %) 0 105 (37)† Venous APS (n; %) 9 (6) 154 (54)† Obstetrical APS (n; %) 168 (89) 89 (31)† Mix APS (n; %) 8 (4) 16 (6) Non-criteria features 16 (9) 141 (49)† (n; %) Obstetrical history Miscarriages (n; %) 66 (35) 18 (6)† Intrauterine deaths 60 (32) 46 (16)† (n; %) Figure 1 Adverse obstetrical events (fetal loss and/or Prematurity 43 (23) 31 (11)† premature birth before the 34 weeks of gestation because of <34 weeks of eclampsia or severe preeclampsia or placental insufficiency) in gestation (n; %) 109 pregnancies of seronegative APS depending on treatment †p<0.05. during the pregnancy and the type (aspirin or aspirin/LMWH Values are numbers with frequencies and means with SD. combination). APS, antiphospholipid syndrome; LMWH, APS, antiphospholipid syndrome. low-molecular weighted heparin. Abisror N, et al. RMD Open 2020;6:e001340. doi:10.1136/rmdopen-2020-001340 3 RMD Open observed in 134 women (47%). Seropositive APS women Table 2 Pregnancy outcome and treatment in had significantly more venous and/or arterial thrombosis seronegative and seropositive APS than seronegative APS women (table 1). Cardiovascular risk factors including arterial hypertension, dyslipidae- Seronegative Seropositive APS APS mia, and/or diabetes mellitus were significantly more pregnancies pregnancies frequent in seropositive APS patients, and the latter (n=108) (n=75) have more non-criteria APS manifestations (livedo race- mosa, thrombocytopenia and migraines). Seronegative APS features APS women were more prone to have obstetrical pheno- Thrombotic APS types, with more frequent intrauterine deaths, miscar- Arterial APS (n; %) 0 20 (27)† riages and early prematurity (table 1). Venous APS (n; %) 8 (7) 42 (56)† For the comparisons of subsequent pregnancies follow- Obstetrical APS (n; %) 93 (86) 36 (48)† ing APS diagnoses, we included 108 seronegative APS and Mix APS (n; %) 6 (6) 18 (24)† 75 seropositive APS women, who had at least one preg- Non-criteria features 18 (17) 34 (45)† nancy after APS diagnosis (table 2). The frequencies of (n; %) treated pregnancies and rates of aspirin-LMWH combina- Previous obstetrical history tion, prednisone and hydroxychloroquine used during Miscarriages (n; %) 49 (45) 8 (11)† the pregnancy were not significantly different in serone- Intrauterine deaths 29 (27) 16 (21) gative and seropositive APS, except for higher rates of (n; %) curative LMWH use in seropositive APS and of aspirin Prematurity <34 weeks 24 (22) 14 (19) alone in seronegative APS. Cumulative incidence of of gestation (n; %) adverse obstetrical events was similar in seronegative Subsequent pregnancy treatments and seropositive APS patients (figure 2), although higher Aspirin (n; %)/aspirin alone 95 (88)/32 (30) 57 (76)†/2 (3)† rates of intrauterine deaths (15% vs 5%; p=0.03), pree- LMWH isocoagulant 63 (58) 39 (52) clampsia (7% vs 16%, p=0.048) and lower live birth term amounts (n; %) (36±3 vs 38±3 weeks of gestation; p=0.04) were noted in LMWH curative amounts 2 (2) 33 (44)† seropositive treated APS. (n; %) Then, we analysed factors associated with fetal loss Aspirin-LMWH (n; %) 65 (60) 55 (73) (<10 weeks of gestation), intrauterine deaths (>10 weeks Prednisone (n; %) 10 (9) 4 (5) of gestation), premature birth (<34 weeks of gestation) Hydroxychloroquine (n; %) 10 (9) 8 (11) and preeclampsia/HELLP syndrome considering all Venous thrombosis (n; %) 0 1 (1) pregnancies of both seropositive and seronegative APS Pregnancy outcome women. The factors analysed in univariate analysis for Preeclampsia/HELLP 7 (7) 12 (16)† these different obstetrical outcomes included: age, sero- syndrome (n; %) positive or seronegative APS status, cardiovascular risk Intrauterin growth 5 (5) 7 (10) factors (obesity, arterial hypertension, diabetes, tobacco restriction (IUGR) use, hereditary thrombophilia), clinical APS phenotype (n; %) (thrombotic, obstetrical or mix), presence of non-criteria Oligoamnios (n; %) 2 (2) 1 (1) APS features (livedo, thrombocytopenia, headaches, Lib- Fetal loss (n; %) 33 (31) 22 (29) man–Sachs endocarditis, etc.), type of therapies during miscarriage/intrauterine 23 (21)/5 (5) 11 (15)/11 the pregnancy (aspirin, LMWH and isocoagulant or cura- deaths (15)† tive amounts, prednisone, hydroxychloroquine), mater- Prematurity <34 weeks of 6 (6) 9 (12) nal adverse obstetrical events (preeclampsia/HELLP, gestation (n; %) thrombosis), fetal complication (IUGR, oligoamnios) Term of fetal loss (weeks of 10±8 13±7 and term of delivery. Considering the risk of fetal loss gestation) (<10 weeks of gestation), in multivariate analyses, no Live births (n; %) 75 (69) 53 (70) differences have been shown with regard to seroposi- Term of live birth (weeks of 38±3 36±3† tive/seronegative APL status and the history of previous gestation) early miscarriage (OR 3.4 [1.34, 9.08] (p=0.01)) and †p<0.05. smoking (OR 4.70 [1.07, 21.01] (p=0.038)) were asso- Values are numbers with frequencies and means with SD. ciated with an increased risk of early fetal loss, while APS, antiphospholipid syndrome; HELLP, hemolysis, Elevated aspirin was associated with a lower risk (OR 0.25 [0.1, Liver enzymes and Low platelet count; LMWH, low-molecular 0.61] (p=0.003)). Considering intrauterine deaths weighted heparin. (>10 weeks of gestation), in multivariate analysis, only previous history of intra-uterine death was significant with OR 4.8 [1.6; 15.6] (p=0.006). the preventive use of LMWH were associated with Considering preeclampsia and HELLP syndrome, in decreased risk (OR at 0.89 [0.81, 0.98] (p=0.007) and multivariate analysis, the age at the APS diagnosis and 0.20 [0.03, 0.96] (p=0.02), respectively). 4 Abisror N, et al. RMD Open 2020;6:e001340. doi:10.1136/rmdopen-2020-001340 Connective tissue diseases tested in this study. Other studies described serone- gative APS considering only major clinical APS cri- teria, without adding APS non-criteria features, with mainly clinical APS features and not all having at least one detectable non-criteria APL. Seronegative APS have been found to present more frequent obstetrical features, in particular recurrent miscar- riages in another case-series, but only with 37% of patients that have detectable non-criteria APL.11 A major limitation of seronegative APS studies is actually the heterogeneity of tested non-criteria APL, the clinical inclusion criteria, the absence of diagnostic criteria; studies of seronegative APS with at least on detectable non-criteria APL are lacking. Non-criteria APL have also been evaluated in seropo- sitive APS patients, considering the potential use to define high-risk subgroups. Thus, anti-PS/PT antibo- dies have been shown to be associated to adverse pregnancy outcome,12 and included in the GAPSS Figure 2 Adverse obstetrical events (fetal loss and/or scale, defining the relapse risk for thrombotic premature birth before the 34 weeks of gestation because of APS.13 Among APS women seeking conception, anti- eclampsia or severe preeclampsia or placental insufficiency) PS/PT antibodies have been found to be an interest- among 183 pregnancies depending on APS seropositive and seronegative status. APS, antiphospholipid syndrome. ing marker for APL-related complications, in particu- lar for IUGR.14 The prevalence of different non-criteria APL in our study varied from 0% for anti-vimentin Considering the occurrence of at least one adverse and IgA aCL antibodies to 37% for anti-PS/PT autoan- obstetrical events among early fetal loss, intrauterine tibodies and could be useful to consider in routine deaths, premature birth and preeclampsia/HELLP syn- screening of the seronegative APS. drome, the multivariate analysis showed that aspirin use In our case series, more than 80% of seronegative APS (OR at 0.29 [0.11, 0.69]; p=0.003) was associated with women have received aspirin and/or LMWH combina- obstetrical outcomes, independently of seropositive or tion during the pregnancy, with a similar rate of com- seronegative APL status. bined aspirin-LMWH to seropositive APS. Seropositive APS seems to have poorer obstetrical outcome, despite more prevalent curative APS amounts. Moreover, DISCUSSION whether combined aspirin-LMWH treatment signifi- In this large European case-series of seronegative APS cantly reduces placenta-mediated complications in with at least one detectable non-criteria APL, we women receiving low-dose aspirin for previous severe described clinical APS features and compared them to preeclampsia diagnosed before 34 weeks of gestation seropositive APS. Seronegative APShave less frequent and no previously recognised APS has been thrombotic and non-criteria features than seropositive challenged.15 16 Data about the management of serone- APS. Pregnancy outcomes of seronegative APS were man- gative APS are quite scarce. We previously reported 65 aged similarly to seropositive APS especially with a similar patients with seronegative APS with at least one non- use of isocoagulant LMWH and combined aspirin-LMWH criteria APL, compared with 83 seropositive APS and treatment during the pregnancy and associated with bet- to the control group without any APL.17 The conven- ter obstetrical outcomes in seronegative APS women than tional aspirin/heparin combination was significantly no treatment. associated with live births in both seropositive and ser- Patients with clinical features of APS considering onegative APS groups, at the difference of women with- Sydney criteria but with negative APL tests are quite out any detectable APL. Our study provides data about usual, and the diagnosis of seronegative APS has the management of seronegative APS during the preg- been introduced for these patients by Hughes and nancy and shows the benefit of aspirin alone or com- Khamashta in 2003.9 10 In this study, 67 patients bined with LMWH to prevent adverse obstetrical with major clinical APS criteria and at least two addi- outcomes. Prospective studies are lacking to determine tional non-criteria features without conventional APL the value and the types of therapies for seronegative were compared with seropositive APS (n=87).10 APS, in particular the need for prophylactic vitamin Thrombotic and obstetrical features were similar in K antagonists therapies in thrombotic seronegative APS. both seronegative and seropositive APS patients, ser- Some important limitations should be discussed onegative APS tended to have more pregnancy mor- such as the retrospective design, the possible inclusion bidity, and non-conventional APL have not been of mainly obstetrical subtypes and the absence of Abisror N, et al. RMD Open 2020;6:e001340. doi:10.1136/rmdopen-2020-001340 5 RMD Open 19 centralised screening of both conventional and non- Department of Gynaecology and Obstetrics and Reproductive Medicine, Tenon criteria APL in our cases. Seronegative and seropositive Hospital, Assistance Publique – Paris Hospitals,Paris, France 20 Service de Médecine Interne et Immunologie Clinique, Centre de Référence des APS were not matched which can account for the differ- Maladies Auto-Immunes Systémiques Rares du Nord et Nord-Ouest (CeRAINO), Univ. ences which have been noted between these groups. Lille, CHU Lille, Lille, France Even thrombotic and obstetrical APS should be 21 Department of Immunology, AP-HP, Hôpital Saint Antoine,Paris, France 22 included, the need for at least one pregnancy, more Immunology Department, Bichat Hospital, APHP, Paris, France 23 frequent non-criteria APL screening after adverse obste- Department of Internal Medicine, University Hospital of Amiens, Amiens, France 24 Université de Paris, INSERM UMR_S1148, Paris cedex 18, France trical event probably could biased the prevalence of 25 Laboratoire d’Hématologie, AP-HP, Hôpital Bichat, Paris cedex 18, France thrombotic subtypes. APS is still a diagnostic challenge, 26 Systemic Autoimmune Diseases Unit, Department of Internal Medicine-1, Vall as no international standardised laboratory tests are d’Hebron University Hospital, Barcelona, Spain 27 available, and it is also conceivable that positive APL Department of Medicine, Faculty of Medicine, Universitat Autönoma de Barcelona, becomes negative over the time. Despite these important Barcelona, Spain limitations, one has to consider that, previously, anti- B2GPI have been added to the laboratory criteria of Acknowledgements We thank the European Forum on Antiphospholipid Antibodies for his help in this study. APS and that new autoantigens target antibodies could Contributors All authors were involved in drafting the article. NAand AM have full be an additional tool to help to the APS diagnosis.11 access to all data in the study and takes responsibility for the integrity of the data and According to the different prevalent of these non- the accuracy of data analysis. Study conception and design: NA, YN, LM, EEV, CDM, criteria APL, in particular, for IgA and anti-vimentin PB, DEP, LC, GK, MB, CJ, PNR, GU, PZ, HB, KP, YB, JAR, OF, AM. Acquisition of data: antibodies, the screening of non-criteria APL could be NA, YN, LM, EV, CDM, PB, DEP, LC, GK, MB, CJ, PNR, GU, PZ, HB, KP, YB, JAR, OF, organised in ‘step by step’ approach. AM. Analysis and interpretation of data: NA, YN, MA, OF, AM. Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors. Competing interests None declared. CONCLUSION Patient consent for publication Not required. Several non-criteria APL can be detected in patients with Ethics approval Ethical committee not required for this observational study clinical features consistent with APS without any conven- according to Helsinki law. tional APL, with various prevalent rates. The detection of Provenance and peer review Not commissioned; externally peer reviewed. non-criteria APL and thus the diagnosis of seronegative APS Data availability statement Data are available in a public, open access repository. could discuss the therapeutic management similar to sero- Supplemental material This content has been supplied by the author(s). It has positive APS, but well-designed controlled studies are not been vetted by BMJ Publishing Group Limited (BMJ) and may not have necessary. been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability Author affiliations and responsibility arising from any reliance placed on the content. Where the 1 Sorbonne Université, AP-HP, Hôpital Saint-Antoine, Service de Médecine Interne content includes any translated material, BMJ does not warrant the accuracy and Inflammation-Immunopathology-Biotherapy Department (DMU 3iD), Paris, and reliability of the translations (including but not limited to local regulations, France clinical guidelines, terminology, drug names and drug dosages), and is not 2 Department of Internal Medicine, AP-HP Nord, Beaujon Hospital, Paris University, responsible for any error and/or omissions arising from translation and adap- Clichy, France tation or otherwise. 3 Department of Surgical Sciences, Obstetrics and Gynecology, University of Torino, Open access This is an open access article distributed in accordance with the Turin, Italy Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which 4 Department of Internal Medicine, Althaia Network Health, Manresa, Barcelona, permits others to distribute, remix, adapt, build upon this work non-commercially, Spain and license their derivative works on different terms, provided the original work is 5 5Autoimmune, Thrombophilic Diseases and Pregnancy Section, Acute Hospital “Dr properly cited, appropriate credit is given, any changes made indicated, and the use Carlos G Durand”, Buenos Aires, Argentina is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/. 6 Department of Immunology, Hospital Universitario 12 de Octubre and Research Institute, Madrid, Spain ORCID iDs 7 Department of Internal Medicine, Vascular and Thrombosis Unit, Rouen University Yann Nguyen http://orcid.org/0000-0002-0866-3824 Hospital, Normandie University, UNIROUEN, INSERM, Rouen, France Lionel Carbillon http://orcid.org/0000-0001-6367-4828 8 Department of Obstetrics and Gynecology, Medical University of Graz, Graz, Austria Eric Hachulla http://orcid.org/0000-0001-7432-847X 9 Service Department of internal medicine, CHU d’Angers, Angers, France Arsène Mekinian http://orcid.org/0000-0003-2849-3049 10 Department of Rheumatology, University Medical Centre Ljubljana, Ljubljana, Slovenia 11 Département de Médecine Vasculaire, Médecine Interne et Pneumologie, CHU de REFERENCES Brest, Hôpital La Cavale Blanche, Brest Cedex, France 1 Mekinian A, Costedoat-Chalumeau N, Masseau A, et al. 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