# Is the current ASAS expert definition of a positive family history useful in identifying axial spondyloarthritis? Results from the SPACE and DESIR cohorts

Zineb Ez-Zaitouni, Andrea Hilkens, Laure Gossec, Inger Jorid Berg, Robert Landewé, Roberta Ramonda, Maxime Dougados, Désirée van Der Heijde,

Floris van Gaalen

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Zineb Ez-Zaitouni, Andrea Hilkens, Laure Gossec, Inger Jorid Berg, Robert Landewé, et al. Is the current ASAS expert definition of a positive family history useful in identifying axial spondyloarthritis? Results from the SPACE and DESIR cohorts. Arthritis Research and Therapy, 2017, 19, pp.118. 10.1186/s13075-017-1335-8. [hal-01546978](https://hal.sorbonne-universite.fr/hal-01546978)

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# Is the current ASAS expert definition of a positive family history useful in identifying axial spondyloarthritis? Results from the SPACE and DESIR cohorts

Zineb Ez-Zaitouni<fnref n="1" />*, Andrea Hilkens<fnref n="1" />, Laure Gossec²,³, Inger Jorid Berg⁴, Robert Landewé⁵, Roberta Ramonda⁶, Maxime Dougados⁷, Désirée van der Heijde<fnref n="1" /> and Floris van Gaalen<fnref n="1" />

**Abstract**

**Background:** The Assessment of SpondyloArthritis international Society (ASAS) definition of a positive family history (PFH) of spondyloarthritis (SpA) includes the following diseases in first- or second-degree relatives: ankylosing spondylitis (AS), acute anterior uveitis (AAU), reactive arthritis (ReA), inflammatory bowel disease (IBD), and psoriasis. However, it is not known if a PFH for each of these diseases contributes to making a diagnosis of axSpA, sacroiliitis on imaging, or fulfilling the ASAS criteria in patients presenting with chronic back pain (CBP). Therefore, the aim of this study was to assess which SpA diseases in family members are associated with human leukocyte antigen B27 (HLA-B27) and axial spondyloarthritis (axSpA) in CBP patients.

**Methods:** CBP patients suspected of axSpA from the SPACE (n = 438) and the DESIR (n = 647) cohort were asked about the presence of SpA diseases in first- or second-degree relatives (AS, AAU, ReA, IBD, and psoriasis). The associations between a PFH and HLA-B27, sacroiliitis on imaging (magnetic resonance imaging (MRI) or radiographs), axSpA diagnosis, and ASAS classification in CBP patients were assessed.

**Results:** In the SPACE and the DESIR cohort, a PFH of AS (odds ratio (OR) 5.9 (95% confidence interval (CI) 3.5–9.9), and OR 3.3 (95% CI 2.1–5.2)) and a PFH of AAU (OR 9.8 (95% CI 3.3–28.9) and OR 21.6 (95% CI 2.9–160.1)) were significantly associated with presence of HLA-B27. Furthermore, in both cohorts a PFH of AS and a PFH of AAU were positively associated with fulfilment of the ASAS criteria, but not with sacroiliitis on imaging. In SPACE but not in DESIR a PFH of AAU was positively associated with axSpA diagnosis. In both cohorts a PFH of ReA, IBD, or psoriasis was not positively associated with HLA-B27 positivity, sacroiliitis on imaging, axSpA diagnosis, or meeting the ASAS criteria for axSpA.

**Conclusions:** In our cohorts, a PFH of AS or AAU is useful for case-finding of axSpA as this is correlated with HLA-B27 carriership. However, as a PFH of ReA, IBD, or psoriasis does not contribute to identifying axSpA in CBP patients, these data suggest that the widely used ASAS definition of a PFH of SpA should be updated.

**Trial registration:** Trial registration number, NCT01648907. Registered on 20 July 2012.

**Keywords:** Family history, Ankylosing spondylitis, Acute anterior uveitis, Reactive arthritis, IBD, Psoriasis, Axial spondyloarthritis, Diagnostic work-up, Chronic back pain

<footnote>* Correspondence: z.ez-zaitouni@lumc.nl</footnote>

<footnote n="1">¹Department of Rheumatology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands</footnote>

<footnote>Full list of author information is available at the end of the article</footnote>
## Background

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease mainly involving the spine and sacroiliac joints. Genetic risk factors play a role in axSpA with human leukocyte antigen B27 (HLA-B27) by far the strongest genetic risk factor for disease [1]. A positive family history (PFH) of SpA has been reported in up to 40% of ankylosing spondylitis (AS) patients and the risk to develop AS in HLA-B27-positive first-degree relatives of HLA-B27-positive AS patients has been estimated to be 16-times higher than that of HLA-B27-positive individuals in the general population [2–5]. As a result, familial aggregation of SpA is considered a risk indicator for the presence of axSpA in patients with chronic back pain (CBP) and is part of several SpA classification criteria sets [6–8].

In the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axSpA, a PFH of SpA is defined as the presence of any of the following diseases in first- or second-degree relatives: AS, acute anterior uveitis (AAU), reactive arthritis (ReA), inflammatory bowel disease (IBD), and psoriasis [8]. This PFH definition is also recommended in diagnosing axSpA, and is incorporated in several referral strategies for CBP patients used by nonrheumatologists [9, 10].

However, only three of these diseases have a documented HLA-B27 association (i.e., AS, AAU, and ReA) and two are not HLA-B27 associated (i.e., IBD and psoriasis) [11–13]. Thus, even though a PFH of SpA is a common finding in axSpA patients it is unknown whether a PFH of each of these diseases contributes equally well to making a diagnosis of axSpA in patients presenting with CBP.

In this study, we present data from two unique early axSpA cohorts: the multinational multicenter SPondyloArthritis Caught Early (SPACE) cohort and the French multicenter DEvenir des Spondylarthropathies Indifférenciées Récentes (DESIR) cohort. In these cohorts of CBP patients with a suspicion of axSpA we have investigated which of the SpA diseases present among family members were associated with HLA-B27, sacroiliitis on imaging, a clinical diagnosis of axSpA, and meeting the ASAS classification criteria for axSpA.

## Methods

### Patient cohorts

The SPACE cohort is a prospective study which includes patients with short-term CBP (≥3 months, ≤2 years, and an onset <45 years) at a minimum age of 16 years from five Rheumatology outpatient clinics in the Netherlands, Norway, and Italy. DESIR is a prospective longitudinal cohort running in 25 centers in France (clinicaltrials.gov, NCT01648907). Patients between the ages of 18 and

50 years with inflammatory back pain (IBP) according to the Calin [14] or Berlin [15] criteria, persisting ≥3 months but <3 years, were included. In addition, the treating rheumatologist had to have a substantial suspicion of axSpA (level of confidence ≥5 on a 0–10 rating scale, where 0 = not confident and 10 = very confident). A detailed description of both cohorts is provided elsewhere [16, 17].

<table><caption>**Table 1** Baseline characteristics and clinical features of CBP patients in the SPACE (n = 438) and DESIR cohorts (n = 647)</caption><thead><tr><th>Characteristic</th><th>SPACE n = 438</th><th>DESIR n = 647</th></tr></thead><tbody><tr><td>Age, years</td><td>31.3 (8.3)</td><td>33.6 (8.6)</td></tr><tr><td>Symptom duration, months</td><td>13.4 (7.4)</td><td>18.1 (10.5)</td></tr><tr><td>Male</td><td>165 (38)</td><td>305 (47)</td></tr><tr><td>IBP</td><td>286 (66)</td><td>647 (100)*</td></tr><tr><td>Good response to NSAIDs<sup>a</sup></td><td>181/420 (43)</td><td>515/643 (80)</td></tr><tr><td>Past history or current symptoms</td><td></td><td></td></tr><tr><td>Peripheral arthritis</td><td>64 (15)</td><td>363 (56)</td></tr><tr><td>Dactylitis</td><td>24 (6)</td><td>83 (13)</td></tr><tr><td>Enthesitis</td><td>89 (20)</td><td>312 (48)</td></tr><tr><td>AAU</td><td>34 (8)</td><td>51 (8)</td></tr><tr><td>IBD</td><td>34 (8)</td><td>23 (4)</td></tr><tr><td>Psoriasis</td><td>51 (12)</td><td>97 (15)</td></tr><tr><td>Elevated CRP (mg/L)/ESR (mm)<sup>b</sup></td><td>123 (28)</td><td>254 (39)</td></tr><tr><td>HLA-B27 positive</td><td>174/436 (40)</td><td>376/646 (58)</td></tr><tr><td>Sacroiliitis, radiography<sup>c</sup></td><td>48/434 (11)</td><td>172 (27)</td></tr><tr><td>Sacroiliitis, MRI<sup>c</sup></td><td>135/431 (31)</td><td>207/636 (33)</td></tr><tr><td>ASAS criteria for axSpA</td><td>203 (46)</td><td>410/634 (65)</td></tr><tr><td>Any positive family history<sup>d</sup></td><td>185 (42)</td><td>249 (39)</td></tr><tr><td>PFH of AS</td><td>90 (21)</td><td>127 (20)</td></tr><tr><td>PFH of AAU</td><td>27 (6)</td><td>29 (5)</td></tr><tr><td>PFH of ReA</td><td>14 (3)</td><td>6 (1)</td></tr><tr><td>PFH of IBD</td><td>33 (8)</td><td>32 (5)</td></tr><tr><td>PFH of Psoriasis</td><td>83 (19)</td><td>129 (20)</td></tr><tr><td>Total number of SpA diseases in first- or second-degree relatives</td><td></td><td></td></tr><tr><td>Number of patients with 1 disease</td><td>135 (73)</td><td>189 (76)</td></tr><tr><td>Number of patients with 2 diseases</td><td>39 (21)</td><td>47 (19)</td></tr><tr><td>Number of patients with ≥3 diseases</td><td>11 (6)</td><td>13 (5)</td></tr></tbody></table>

Unless specified otherwise, results are presented as mean ± SD or number (%)

*Inclusion criterion

aBack pain not present anymore or is much better 24–48 hours after a full dose of NSAID

bValues greater than the upper limit of normal

cImaging based on local reading. of sacroiliac joints

dPresence in first- or second-degree relatives of any of the following: AS, AAU, ReA, IBD, or psoriasis

AAU acute anterior uveitis, AS ankylosing spondylitis, ASAS axSpA criteria, Assessment of Spondyloarthritis international Society criteria for axial Spondyloarthritis, CBP chronic back pain, CRP C-reactive protein, ESR erythrocyte sedimentation rate, HLA-B27 human leucocyte antigen B27, IBD inflammatory bowel disease, IBP inflammatory back pain, MRI magnetic resonance imaging, NSAID non-steroidal anti-inflammatory drug, PFH positive family history, ReA reactive arthritis, SpA spondyloarthritis
<table><caption>**Table 2** Association of family history manifestations with HLA-B27 in CBP patients in the SPACE (n = 438) and DESIR cohorts (n = 647)</caption><thead><tr><th rowspan="2"></th><th colspan="4">SPACE*</th><th colspan="4">DESIR**</th></tr><tr><th>HLA-B27 + n = 174</th><th>HLA-B27- n = 262</th><th>OR (95% CI)</th><th>P value</th><th>HLA-B27 + n = 376</th><th>HLA-B27- n = 270</th><th>OR (95% CI)</th><th>P value</th></tr></thead><tbody><tr><td>Any PFH</td><td>97</td><td>87</td><td>2.5 (1.7–3.8)</td><td>&lt;0.001</td><td>158</td><td>91</td><td>1.4 (1.0–2.0)</td><td>0.032</td></tr><tr><td>AS</td><td>65</td><td>24</td><td>5.9 (3.5–9.9)</td><td>&lt;0.001</td><td>100</td><td>27</td><td>3.3 (2.1–5.2)</td><td>&lt;0.001</td></tr><tr><td>AAU</td><td>23</td><td>4</td><td>9.8 (3.3–28.9)</td><td>&lt;0.001</td><td>28</td><td>1</td><td>21.6 (2.9–160.1)</td><td>0.003</td></tr><tr><td>ReA</td><td>5</td><td>9</td><td>0.8 (0.3–2.5)</td><td>0.745</td><td>1</td><td>5</td><td>0.1 (0.01–1.2)</td><td>0.075</td></tr><tr><td>IBD</td><td>12</td><td>21</td><td>0.9 (0.4–1.8)</td><td>0.666</td><td>17</td><td>15</td><td>0.8 (0.4–1.6)</td><td>0.551</td></tr><tr><td>Psoriasis</td><td>34</td><td>48</td><td>1.1 (0.6–1.8)</td><td>0.750</td><td>69</td><td>60</td><td>0.8 (0.5–1.2)</td><td>0.225</td></tr></tbody></table>

*Two patients with unknown HLA-B27 status

**One with patient unknown HLA-B27 status

AAU acute anterior uveitis, AS ankylosing spondylitis, CBP chronic back pain, CI confidence interval, HLA-B27 human leucocyte antigen B27, IBD inflammatory bowel disease, OR odds ratio, PFH positive family history (manifestation in first- or second-degree relatives), ReA reactive arthritis

Both studies were approved by local medical ethics committees. All participants provided prior written informed consent.

## Clinical data collection

All patients underwent a diagnostic work-up according to a fixed protocol which includes physical examination, laboratory assessments (HLA-B27, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR)), and magnetic resonance imaging (MRI) as well as radiographs of sacroiliac joints. The presence and history of clinical SpA features were assessed: IBP, good response to nonsteroidal anti-inflammatory drugs (NSAIDs), peripheral arthritis, dactylitis, enthesitis, AAU, IBD, and psoriasis. Patients were asked about the presence of any of the following SpA diseases in first- or second-degree relatives: AS, AAU, ReA, IBD, and psoriasis. For each SpA disease the possible answers were “yes”, “no” or “unknown/uncertain”. A PFH was defined as the presence of ≥1 SpA-related disease in first- (mother, father, sister, brother, daughter, son) or second-degree

relatives (aunt, uncle, niece, nephew, grandmother, and grandfather) reported by the patient [8].

In the SPACE cohort, axSpA was diagnosed by the treating rheumatologist. In the DESIR cohort axSpA diagnosis was defined as the level of confidence regarding diagnosis of ≥8 on a 0–10 numerical rating scale (where 0 = not confident at all and 10 = very confident). The ASAS axSpA classification criteria were used to classify patients.

## Data analysis

Baseline demographic and clinical characteristics are presented using descriptive statistics for both the SPACE and DESIR cohorts. The association between each PFH disease and HLA-B27 in patients was assessed using the Chi-squared test. Similar analyses were performed for the assessment of the association between each PFH disease and a clinical diagnosis of axSpA, sacroiliitis on imaging (defined as either sacroiliitis on MRI,

<table><caption>**Table 3** Association of family history manifestations with the fulfilment of ASAS axSpA criteria in the SPACE cohort and DESIR cohorts</caption><thead><tr><th rowspan="3"></th><th colspan="4">Fulfilment of ASAS axSpA criteria</th></tr><tr><th colspan="2">SPACE</th><th colspan="2">DESIR</th></tr><tr><th>OR (95% CI)</th><th>P- value</th><th>OR (95% CI)</th><th>P- value</th></tr></thead><tbody><tr><td>Any PFH</td><td>2.1 (1.4-3.1)</td><td>&lt;0.001</td><td>1.3 (1.0-1.9)</td><td>0.091</td></tr><tr><td>AS</td><td>3.3 (2.0-5.3)</td><td>&lt;0.001</td><td>2.1 (1.3-3.3)</td><td>&lt;0.001</td></tr><tr><td>AAU</td><td>7.4 (2.5-21.7)</td><td>&lt;0.001</td><td>5.0 (1.5-16.7)</td><td>0.009</td></tr><tr><td>ReA</td><td>0.6 (0.2-1.9)</td><td>0.421</td><td>0.3 (0.05-1.5)</td><td>0.132</td></tr><tr><td>IBD</td><td>1.1 (0.5-2.2)</td><td>0.798</td><td>0.8 (0.4-1.6)</td><td>0.521</td></tr><tr><td>Psoriasis</td><td>1.2 (0.8-2.0)</td><td>0.388</td><td>1.2 (0.8-1.8)</td><td>0.464</td></tr></tbody></table>

Any PFH, any family history manifestation in first- or second-degree relatives; AS ankylosing spondylitis, AAU acute anterior uveitis, ReA reactive arthritis, IBD inflammatory bowel disease, OR odds ratio, 95% CI 95% confidence interval

<table><caption>**Table 4** PFH of diseases in first- or second-degree relatives of CBP patients meeting the ASAS axSpA criteria, stratified according to HLA-B27 status</caption><thead><tr><th rowspan="2">Positive family history</th><th colspan="2">SPACE cohort n = 201*</th><th colspan="2">DESIR cohort n = 409**</th></tr><tr><th>HLA-B27+</th><th>HLA-B27-</th><th>HLA-B27+</th><th>HLA-B27-</th></tr></thead><tbody><tr><td>Any PFH</td><td>90 (45%)</td><td>14 (7%)</td><td>145 (35%)</td><td>24 (6%)</td></tr><tr><td>AS</td><td>59 (29%)</td><td>2 (1%)</td><td>92 (23%)</td><td>5 (1%)</td></tr><tr><td>AAU</td><td>22 (11%)</td><td>1 (1%)</td><td>26 (6%)</td><td>0 (0)</td></tr><tr><td>ReA</td><td>4 (1%)</td><td>1 (1%)</td><td>1 (0.2%)</td><td>1 (0.2%)</td></tr><tr><td>IBD</td><td>11 (6%)</td><td>5 (3%)</td><td>14 (3%)</td><td>5 (1%)</td></tr><tr><td>Psoriasis</td><td>32 (16%)</td><td>9 (5%)</td><td>65 (16%)</td><td>20 (5%)</td></tr></tbody></table>

*Two hundred and three patients fulfilled ASAS-criteria, two with unknown HLA-B27 status

**Four hundred and ten patients fulfilled ASAS-criteria, one with unknown HLA-B27 status

AAU acute anterior uveitis, AS ankylosing spondylitis, ASAS axSpA Assessment of Spondyloarthritis international Society criteria for axial spondyloarthritis, HLA-B27 human leucocyte antigen B27, IBD inflammatory bowel disease, PFH positive family history (manifestation in first- or second-degree relatives), ReA reactive arthritis
radiographs, or on both modalities by local reading),
and the fulfilment of the ASAS axSpA classification
criteria.

Statistical testing was performed using Stata SE v.14
(StataCorp LP, College Station, TX, USA).

Results

For the current analyses, 438 patients from the SPACE
cohort and 647 patients from the DESIR cohort with
complete data at baseline were used (Table 1). Several
baseline characteristics differed between the two co-
horts, mainly reflecting differences in inclusion criteria.
In both cohorts, the distribution of all PFH diseases (AS,
AAU, ReA, IBD, and psoriasis) in first- or second-degree
relatives were similar.

In both the SPACE and DESIR cohort, any PFH, a
PFH of AS, and a PFH of AAU were significantly asso-
ciated with HLA-B27 in CBP patients (Table 2). In
multivariable analyses, a PFH of AS or AAU were
independently associated with HLA-B27 positivity
(data not shown). However, in neither cohort was a
PFH of ReA, IBD, or psoriasis associated with HLA-
B27-positivity.

To investigate whether the presence of a PFH for any
of the diseases in relatives is associated with sacroiliitis,
a clinical diagnosis of axSpA, or a positive ASAS classifi-
cation, similar analyses were performed. In both cohorts,
neither ‘any PFH’ nor a separate PFH of a disease were
associated with sacroiliitis (Additional file 1). In SPACE
but not in DESIR a PFH of AAU was positively associ-
ated with axSpA diagnosis (Additional file 2). While a
PFH of AS or AAU had a significant positive associ-
ation with fulfilment of the ASAS criteria, such an as-
sociation was not found for a PFH of ReA, IBD, or
psoriasis in the SPACE and DESIR cohorts (Table 3).

In addition, the relative contribution of HLA-B27 was
investigated among patients who were classified according
to the ASAS criteria. A total of 203 (46%) patients from
the SPACE cohort and 410 (63%) patients from the DESIR
cohort fulfilled the ASAS criteria for axSpA, and 156
(77%) and 347 (85%) patients were HLA-B27 positive, re-
spectively (Table 4). A PFH was reported more frequently
in HLA-B27-positive patients than in HLA-B27-negative
patients meeting the ASAS classification criteria (SPACE
45% vs 7% and DESIR 35% vs 6%).

Discussion

To our knowledge this is the first study to investigate the
usefulness of the separate SpA diseases in a PFH as de-
fined for the ASAS classification criteria. In two independ-
ent cohorts of predominantly Caucasoid Europeans, we
found that in CBP patients suspected of axSpA a PFH
of ReA, IBD, or psoriasis were neither associated with
HLA-B27 positivity, nor with sacroiliitis, a diagnosis of

axSpA, or fulfilment of the ASAS criteria. In contrast, a
PFH of AS or AAU was strongly correlated with HLA-
B27 carriership.

IBD and psoriasis are generally not HLA-B27-
associated diseases, but ReA has been reported to be
associated with HLA-B27 in a secondary care setting,
although in population-based studies the prevalence of
HLA-B27 in ReA was comparable to that of the general
population [12, 18]. A possible explanation for the ab-
sence of the association between ReA and HLA-B27 in
our study is that the (self)-reported prevalence of ReA
in family members of patients in the SPACE and DESIR
cohort was low, suggesting underreporting.

It is important to emphasize that the current study was
performed in patients with predominantly axial symp-
toms. Although only a PFH of AS or AAU have been
shown to be independently associated with HLA-B27, this
does not mean that a PFH of the other SpA diseases is al-
ways irrelevant [19]. For example, the presence of psoriasis
in relatives could be relevant in a patient with peripheral
symptoms suspected of psoriatic arthritis [20].

A strength of this study is the use of two large early
axSpA cohorts in which all patients were assessed fol-
lowing a similar protocol which allowed for replication
of findings. Strikingly similar prevalences of PFH were
found in both cohorts which adds to the credibility of
the data. The major limitation of this study, however, is
that the diagnosis in relatives (the PFH) is solely based
on patients' information which may have led to either
under- or overestimation of a PFH. However, this is
similar to most clinical settings in which PFH is also
mostly based on self-reporting. Moreover, subdividing a
PFH into five different diseases meant that a PFH of, for
instance, AAU or ReA was uncommon.

Conclusions

In conclusion, in our two cohorts a PFH of ReA, IBD,
and psoriasis does not contribute to diagnosing axSpA
in CBP patients suspected of axSpA. A PFH of AS or
AAU may be useful in case-finding in low prevalence
settings, such as general practice, as these are correlated
with HLA-B27 carriership. When replicated, preferably
in other regions of the world in patients with a different
genetic background, it is justified to remove a PFH of
ReA, IBD, and psoriasis from the current ASAS definition
of a positive PFH relevant for axSpA.

Additional files

**Additional file 1: Table S1.** Association of family history manifestations with any positive imaging (sacroiliitis on MRI or radiographs) in the SPACE cohort and DESIR cohorts. (DOCX 19 KB)

**Additional file 2: Table S2.** Association of family history manifestations with clinical diagnosis in the SPACE cohort and DESIR cohorts. (DOCX 19 kb)
**Abbreviations**

AAU: Acute anterior uveitis; AS: Ankylosing spondylitis; ASAS: Assessment of SpondyloArthritis international Society; axSpA: Axial spondyloarthritis; CBP: Chronic back pain; HLA-B27: Human leukocyte antigen B27; IBD: Inflammatory bowel disease; IBP: Inflammatory back pain; MRI: Magnetic resonance imaging; PFH: Positive family history; ReA: Reactive arthritis

**Acknowledgements**

The DESIR cohort was sponsored by the Département de la Recherche Clinique et du Développement de l'Assistance Publique-Hôpitaux de Paris. This study is conducted under the umbrella of the French Society of Rheumatology and INSERM (Institut National de la Santé et de la Recherche Médicale). The database management is performed within the Department of Epidemiology and Biostatistics (Professor Paul Landais, D.I.M., Nîmes, France). An unrestricted grant from Pfizer was allocated for the 10 years of the follow-up of the recruited patients. The authors thank the different regional participating centers: Pr. M. Dougados (Paris, Cochin B), Pr. A. Kahan (Paris, Cochin A), Pr. O. Meyer, Pr. P. Dieudé (Paris, Bichat), Pr. P. Bourgeois, Pr. L. Gossec (Paris, La Pitié Salpetrière), Pr. F. Berenbaum (Paris, Saint Antoine), Pr. P. Claudepierre (Créteil), Pr. M. Breban (Boulogne Billancourt), Dr. B. Saint-Marcoux (Aulnay-sous-Bois), Pr. P. Goupille (Tours), Pr. J-F. Maillefert (Dijon), Dr. X. Xuéchal, Dr. E. Dernis (Le Mans), Pr. D. Wendling (Besançon), Pr. B. Combe (Montpellier), Pr. L. Euller-Ziegler (Nice), Pr. P. Orcel, Dr. P. Richette (Paris, Lariboisière), Pr. P. Lafforgue (Marseille), Dr. P. Boumier (Amiens), Pr. M. Soubrier (Clermont-Ferrand), Dr. N. Mehsen (Bordeaux), Pr. D. Loeuille (Nancy), Pr. R-M. Flipo (Lille), Pr. A. Saraux (Brest), Dr. S. Pavy (Le Kremlin Bicêtre), Pr. A. Cantagrel (Toulouse), Pr. O. Vittecoq (Rouen). The authors also thank URC-CIC Paris Centre for the coordination and monitoring of the study.

**Funding**

This work was supported by an unrestricted grant from MSD. MSD was not involved in the design of the study, acquisition, analysis, or interpretation of the data, or drafting the manuscript.

**Availability of data and materials**

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

**Authors' contributions**

ZE-Z, DvdH, and FvG were responsible for study conception and design. ZE-Z, AH, LG, IJB, RL, RR, MD, and FvG were responsible for acquisition of the data. ZE-Z, AH, DvdH, and FvG participated in interpretation and analysis of the data. ZE-Z drafted and wrote the manuscript. ZE-Z, AH, LG, IJB, RL, RR, MD, DvdH, and FvG were involved in critically revising the manuscript for important intellectual content. All authors read and approved the final manuscript.

**Authors' information**

All authors read and approved this manuscript.

**Competing interests**

The authors declare that they have no competing interests.

**Consent for publication**

Not applicable.

**Ethics approval and consent to participate**

The SPACE cohort has been approved by the medical ethical committee of the Leiden University Medical Center (reference number: P08.105). DESIR has been approved by the Île de France III Ethics Committee (reference number: 2457). All necessary consent approval was obtained from any patient involved in the study.

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**Author details**

Received: 17 March 2017 Accepted: 15 May 2017

Published online: 31 May 2017

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