Background: Undifferentiated arthritis (UA) is
defined as cases of inflammatory arthritis where no definitive
diagnosis can be made, and that may evolve into a chronic
inflammatory disease over time or result in persistent drug-free
remission.

背景: 
未分化关节炎(UA)被定义为有炎性关节炎但尚不能明确诊断，而且随时间进展可能演变成慢性炎性疾病，或转化为持续的无药缓解。

Objectives: In this study
we investigated the 2-year disease course in
patients with poly-, oligo- and monoarticular UA, with the main
outcomes being 1) fulfillment of the 2010 ACR/EULAR RA
classification criteria, 2) absence of clinical synovitis without
use of DMARDs and 3) final clinical diagnosis.

目的: 
在本研究中，我们调查了多、寡和单关节UA患者在2年间的演变。主要观察结局是：1)患者符合2010年ACR/
EULAR
RA分类标准，2)不使用DMARDs且无临床滑膜炎，3)最终的临床诊断。

Methods: Patients (18-75 years old)
with ≥1
swollen joint of <16 weeks duration were included in the
multi-center observational study NOR-VEAC (Norwegian Very Early
Arthritis Cohort) and followed for 2 years. Patients with arthritis
due to trauma, septic arthritis, crystal arthritis and
osteoarthritis were excluded. The study included 1118 patients in
total. Patients with a clinical diagnosis of a rheumatic disease
other than RA (N=338) or fulfilling the 2010 ACR/EULAR RA criteria
(N=261) at baseline and those without follow-up data (N=24) were
excluded from the current analyses. Absence of clinical synovitis
was defined as no swollen joints at last
visit.

方法: 
挪威多中心观察性研究——极早期关节炎队列(NOR-VEAC)纳入≥1个肿胀关节、病程<16周的患者(18-75岁)，并随访2年。排除因外伤导致的关节炎、化脓性关节炎、晶体性关节炎和骨关节炎。该研究共纳入1118例患者。在基线时诊断为RA的有338例，符合ACR/EULAR2010版RA分类标准的有261例。本研究排除那些基线临床诊断为其它风湿性疾病的患者以及那些没有随访数据(n=24)的患者。末次随访时无肿胀关节被定义为无临床滑膜炎。

Results: Among the 495 patients who were
denoted UA, 60 (12.1%) patients had polyarthritis (PA), 179 (36.2%)
oligoarthritis (OLA) and 256 (51.7%) monoarthritis (MA) at
baseline. Mean (SD) age was 46.6 (14.6) yrs, 54.1% were females and
median (25, 75 perc.) duration of joint swelling was 29 (10, 62)
days. Only 34 (6.9%) of the 495 UA patients were classified as RA
during follow-up, including 8.9% of those presenting as OLA and
13.3% of those presenting as PA. Conversely, among patients later
classified as RA, 47.1% were OLA patients and 23.5% PA patients at
inclusion. 50.0% of the OLA patients who later fulfilled the RA
criteria were seropositive, while none of the PA patients were. The
most frequently affected joints in the OLA patients fulfilling the
RA criteria were PIP (31.3%), MCP (25.0%), knees (31.3%) and wrists
(31.3%). Only 86 of 495 patients used DMARDs during follow-up
(38.3% of all PA patients, 20.1% OA patients and 10.4% of MA
patients). 41.7%, 63.8% and 76.6% of those presenting as PA, OLA
and MA, respectively, achieved absence of clinical synovitis at
final follow-up visit without use of DMARDs. The most frequent
final clinical diagnosis in PA, OLA and MA patients was UA (40.0%,
50.1% and 68.3%, respectively). Figure 1 shows the distribution of
clinical diagnoses at last visit.

结果: 
基线时，初诊为UA的495例患者中，60例(12.1％)为多关节炎(PA)，179例(36.2％)为寡关节炎(OLA)，256例(51.7％)单关节炎(MA)。平均(SD)年龄为46.6(14.6)岁，54.1％为女性，平均关节肿胀时间(25，75
%)为29(10，62)天。495例UA患者中只有34例(6.9％)在随访过程中被诊断为RA，确诊RA时表现为OLA的比例为8.9％，表现为PA的比例为13.3％。与此相反，在后来归类为RA的患者中，起始表现为OLA的比例为47.1％，PA的比例为23.5％。后来符合RA分类标准的OLA患者中，50.0％为血清学阳性，而演变为RA的PA患者中起初没有一个是血清学阳性。满足RA分类标准的OLA患者中最常见受累关节包括PIP(31.3％)、MCP(25.0％)、膝(31.3％)和手腕(31.3％)。只有86例患者在随访期间使用DMARDs
(PA患者38.3％，OA患者20.1％和MA患者10.4％)。
在末次随访时停用DMARDs且无临床滑膜炎的患者比例：
PA-41.7％,
OLA-63.8％，MA-76.6%。PA、OLA和MA患者最常见的最终临床诊断
为UA，比例分别为40.0％，50.1％和68.3％。图1显示了末次随访时临床诊断的分布。

Conclusions:
Less than 1/5 of all the
UA patients started DMARDs, and only 6.9% of the UA patients were
classified as RA during follow-up, including 9% of those presenting
as OLA and 13% of those presenting as PA. Nearly half of patients
later classified as RA were patients with OLA at inclusion,
however, 64% of OLA cases resolved without ever using DMARDs. The
proportion with a final clinical diagnosis of UA was high
irrespective of poly-, oligo- or monoarticular
presentation.

结论: 不到1/5的UA患者开始使用DMARDs，只有6.9％的UA患者在随访期间被归类为RA，其中包括9％OLA患者和13％的PA患者。近半数的OLA患者后来被归类为RA，然而，64％的OLA患者在未曾使用DMARDs的情况下自动缓解了。不论多、寡、或单关节炎患者，最终诊断仍为UA的比例都是最高的。