SEARCH

SEARCH BY CITATION

Abstract

  1. Top of page
  2. Abstract
  3. PATIENTS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

Objective

To evaluate the interobserver agreement of ultrasonographic assessment of finger and toe joints in patients with rheumatoid arthritis (RA) by 2 investigators with different medical backgrounds.

Methods

Ultrasonography and clinical examination were performed on 150 small joints of 30 patients with active RA. A General Electric LOGIQ 500 ultrasound unit with a 7–13-MHz linear array transducer was used. In each patient, 5 preselected small joints (second and third metacarpophalangeal, second proximal interphalangeal, first and second metatarsophalangeal) were examined independently on the same day by 2 ultrasound investigators (an experienced musculoskeletal radiologist and a rheumatologist with limited ultrasound training). Joint effusion, synovial thickening, bone erosions, and power Doppler signal were evaluated in accordance with an introduced 4-grade semiquantitative scoring system, on which the investigators had reached consensus prior to the study.

Results

Exact agreement between the 2 observers was seen in 91% of the examinations with regard to bone erosions, in 86% with regard to synovitis, in 79% with regard to joint effusions, and in 87% with regard to power Doppler signal assessments. Corresponding intraclass correlation coefficient values were 0.78, 0.81, 0.61, and 0.72, respectively, while unweighted kappa values were 0.68, 0.63, 0.48, and 0.55, respectively. Ultrasonography showed signs of inflammation in 94 joints, while clinical assessment revealed tenderness and/or swelling in 64 joints.

Conclusion

An experienced radiologist and a rheumatologist with limited ultrasound training achieved high interobserver agreement rates for the identification of synovitis and bone erosions, using an introduced semiquantitative scoring system for ultrasonography of finger and toe joints in RA. Signs of inflammation were more frequently detected with ultrasound than with clinical examination. Ultrasonography may improve the assessment of RA patients by radiologists and rheumatologists.

Accurate assessment of disease activity and joint damage in rheumatoid arthritis (RA) is essential in the clinical management of RA patients and in RA clinical trials. A number of studies have described improved sensitivity for detection of joint effusion, synovitis, and bone erosions in RA joints with the use of ultrasound (US) as compared with conventional clinical and radiologic methods (1–3). Because ultrasonography is a relatively easily accessible and lowcost method, the technique can be used not only by radiologists, but also by trained rheumatologists. Examination of RA joints by US therefore has the potential to become a rheumatologic bedside procedure for assessment of early inflammatory and destructive joint pathology. The dependence on skilled operators, potential problems with reproducibility of results, and poor objective documentation of findings are often mentioned as main disadvantages of musculoskeletal US (4, 5).

Despite increasing evidence of the potential applications of ultrasonography in the evaluation of arthritic joints, data on its accuracy and reproducibility remain very limited. In RA, involvement of the small joints of the hands and feet is frequent and occurs early in the course of the disease (6). Consequently, reliable assessment of these joints is of major importance. Both of these joint groups are accessible for assessment by US.

The main aim of the present study was to assess the agreement between independent investigators with different specialty backgrounds regarding US assessment of inflammatory and destructive changes in finger and toe joints in patients with RA. A system of semiquantitative scoring of the analyzed parameters was introduced. Furthermore, the relationship between clinical and US findings was explored.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. PATIENTS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

Patients.

One hundred fifty joints of 30 patients with active RA (fulfilling the 1987 American College of Rheumatology [formerly, the American Rheumatism Association] criteria for RA [7]) were included in the study. The mean age of the RA patients was 53 years (range 23–71), the mean disease duration was 5.5 years (range 0–20), and the female:male ratio was 3:1. Active disease was defined as clinically assessed tenderness and/or swelling of at least 3 small joints of the hands and feet, as assessed by the referring physician. Examinations were performed in each patient on 5 preselected small joints of the hands and feet: the second and third metacarpophalangeal (MCP) joints, second proximal interphalangeal (PIP) joint, and first and second metatarsophalangeal (MTP) joints. We selected these 5 joints because their accessibility for assessment by US was considered representative of all of the small joints of the hands and feet. All patients were recruited from an outpatient hospital–based arthritis clinic. The study was conducted in accordance with the Declaration of Helsinki and approved by the local ethics committee. A signed informed consent was obtained from each participating person.

Ultrasonography.

B-mode and power Doppler US (a technique suitable for examination of slow blood flow and flow in small vessels) was performed with a General Electric LOGIQ 500 unit (General Electric Medical Systems, Milwaukee, WI) by means of a 7–13-MHz linear array transducer. The B-mode frequency used was 11 MHz. The power Doppler settings were as follows: frequency of 6.6 MHz, pulse repetition frequency of 1 kHz, and low wall filter (150 Hz). The color gain was set at the level at which noise artifacts appeared and then gradually reduced, until only a flow signal, if present, was left.

Joint effusion, synovitis, bone erosions, and power Doppler signal in the synovial membrane of the preselected joints were evaluated and classified on 4-grade semiquantitative scales. The selected parameters were defined as follows. Joint effusion was defined as a compressible anechoic intracapsular area (0 = no effusion, 1 = minimal amount of joint effusion, 2 = moderate amount of joint effusion [without distension of the joint capsule], 3 = extensive amount of joint effusion [with distension of the joint capsule]) (Figure 1). Synovitis was defined as a noncompressible hypoechoic intracapsular area (synovial thickening) (0 = no synovial thickening, 1 = minimal synovial thickening [filling the angle between the periarticular bones, without bulging over the line linking tops of the bones], 2 = synovial thickening bulging over the line linking tops of the periarticular bones but without extension along the bone diaphysis, 3 = synovial thickening bulging over the line linking tops of the periarticular bones and with extension to at least one of the bone diaphyses) (Figure 2). Bone erosions were defined as changes in the bone surface of the area adjacent to the joint (0 = regular bone surface, 1 = irregularity of the bone surface without formation of a defect seen in 2 planes, 2 = formation of a defect in the surface of the bone seen in 2 planes, 3 = bone defect creating extensive bone destruction) (Figure 3). Power Doppler signal was, in our study, used to display flow signal in the synovium (0 = no flow in the synovium, 1 = single vessel signals, 2 = confluent vessel signals in less than half of the area of the synovium, 3 = vessel signals in more than half of the area of the synovium) (8) (Figure 4).

thumbnail image

Figure 1. Joint effusion on ultrasonography. A, Grade 0 = no fluid; B, grade 1 = minimal amount of fluid (arrow); C, grade 2 = moderate amount of fluid (without distension of the joint capsule) (arrows); D, grade 3 = extensive amount of fluid (with distension of the joint capsule) (arrow).

Download figure to PowerPoint

thumbnail image

Figure 2. Synovial changes on ultrasonography. A, Grade 0 = no synovial thickening; B, grade 1 = minimal synovial thickening (filling the angle between the periarticular bones, without bulging over the line linking tops of the bones [arrow]); C, grade 2 = synovial thickening bulging over the line linking tops of the periarticular bones but without extension along the bone diaphysis (arrow); D, grade 3 = synovial thickening bulging over the line linking tops of the periarticular bones and with extension to at least one of the bone diaphyses (arrows).

Download figure to PowerPoint

thumbnail image

Figure 3. Bone changes scored with ultrasonography, with each joint visualized in 2 planes (longitudinal and transverse). A and B, Grade 0 = regular bone surface; C and D, grade 1 = irregularity of the bone surface without formation of a defect seen in 2 planes (arrow); E and F, grade 2 = formation of a defect in the surface of the bone seen in 2 planes (arrow); G and H, grade 3 = bone defect creating extensive bone destruction (arrow).

Download figure to PowerPoint

thumbnail image

Figure 4. Power Doppler signal. A, Grade 0 = no flow in the synovium; B, grade 1 = single vessel signals; C, grade 2 = confluent vessel signals in less than half of the area of the synovium; D, grade 3 = vessel signals in more than half of the area of the synovium.

Download figure to PowerPoint

In our study, we considered grades 0–1 of joint effusion, synovitis, and bone erosions to be normal/probably normal, while grades 2–3 indicated definite pathologic changes. With regard to power Doppler signal, grade 0 was considered normal, while grades 1–3 were considered to be definitely pathologic (9). Each examination took ∼15 minutes.

Investigators.

Two independent investigators performed the US examinations. One investigator was a radiologist with extensive experience in musculoskeletal US (MC-P) and the other was a rheumatologist (MS) with experience from 50 supervised US examinations of hand and foot joints of RA patients (i.e., examination of 500 MCP joints, 500 IP and PIP joints, and 500 MTP joints). Prior to the study, the investigators reached consensus with regard to the evaluation scales. The observations of the rheumatologist (MS) were used for comparison with clinical findings.

Clinical examination.

On the same day as the US examination, the clinical disease activity in the small joints of the hands and feet (presence or absence of swelling and tenderness) was assessed by an experienced rheumatologist (SJ). The number and localization of swollen and/or tender joints were determined. The clinician and the 2 US investigators were blinded to each other's findings.

Statistical analysis.

Interobserver agreement was estimated using calculations of intraclass correlation coefficients (ICC) (2-way mixed effects model, consistency definition), unweighted kappa statistics, and overall agreement (defined as the percentage of observed exact agreements) by means of the statistical software package SPSS, release 9.0.1 (Chicago, IL). A Bland-Altman plot, a graphic representation illustrating repeatability of observations, was used to show the relationship between the results of the 2 US investigators.

RESULTS

  1. Top of page
  2. Abstract
  3. PATIENTS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

Interobserver agreement between US investigators.

One hundred fifty small joints of 30 RA patients were examined by the 2 US investigators. Analyses of interobserver agreement, with all joints considered together, are given in Table 1.

Table 1. Interobserver agreement between the 2 ultrasound investigators, as measured by 3 different statistical methods*
 ICCKappaOverall agreement, %
  • *

    Values are the mean intraclass correlation coefficient (ICC), unweighted kappa, or overall percentage of agreement for the examined parameters.

Bone erosions0.780.6891
Synovitis0.810.6386
Joint effusion0.610.4879
Power Doppler signal0.720.5587

The ICC and unweighted kappa estimations for the examined parameters showed a moderate-to-good correlation (0.61–0.81 and 0.48–0.68, respectively) between the US investigators. The overall agreement was high (79–91%). ICC values for each joint are shown in Table 2. For 3 of the 4 parameters, the lowest ICC was achieved for assessment of the third MCP, and for 2 of the 4 parameters, the highest ICC was achieved for assessment of the second MCP. In the individual joints, ICC values were as follows: for the second MCP, ICCs ranged 0.77–0.92 (mean 0.85), for the third MCP, 0.42–0.79 (mean 0.57), for the second PIP, 0.72–0.80 (mean 0.75), for the first MTP, 0.49–0.85 (mean 0.74), and for the second MTP, 0.58–0.89 (mean 0.77). Bland-Altman plots (see Figure 5) showed a good agreement between the 2 US investigators, since no systematic differences in their scores were found (mean differences between −0.21 and 0.05).

Table 2. Mean intraclass correlation coefficients for all examined parameters in the respective joints*
JointIntraclass correlation coefficient
Bone erosionsSynovitisEffusionPower Doppler
  • *

    MCP = metacarpophalangeal; PIP = proximal interphalangeal; MTP = metatarsophalangeal.

  • The missing value reflects too few positive findings to estimate an intraclass correlation value.

MCP 20.920.770.850.84
MCP 30.610.790.420.45
PIP 20.720.800.73
MTP 10.790.810.490.85
MTP 20.850.890.580.77
thumbnail image

Figure 5. Distribution of the 4-grade semiquantitative scorings by the 2 investigators (MC-P and MS) on the Bland-Altman plot for A, bone erosions, B, synovitis, C, joint effusion, and D, power Doppler examination. Values adjacent to solid circles are the number of joints scored to achieve the average.

Download figure to PowerPoint

US versus clinical examinations.

Table 3 shows the results of the US evaluation versus clinical assessment of the preselected 150 small joints. Joint effusion and/or synovitis were visualized with B-mode US in 94 of 150 joints, while only 64 joints presented signs of inflammation on the clinical assessment (swelling and/or tenderness). The US and clinical assessment findings were in agreement on the presence of signs of inflammation in 46 joints (31%) and on the absence of signs of inflammation in 38 joints (25%). In 48 joints (32%), signs of inflammation (effusion or synovitis) on US were found in clinically uninflamed joints, whereas no signs of inflammation were seen by US in 18 joints (12%) in which the clinician described swelling and/or tenderness. In 3 of these 18 joints (2% of all joints assessed), both clinical swelling and tenderness were registered by the clinician.

Table 3. Clinical joint assessment performed on 150 small joints of 30 rheumatoid arthritis patients by an experienced rheumatologist versus ultrasonographic findings of an observer who had a short training period*
Ultrasonographic assessmentClinical assessment
Swelling and tendernessOnly swellingOnly tendernessNo swelling or tenderness
  • *

    Values are the no. of joints with the examined parameter.

Synovitis and joint effusion1224
Only synovitis2461142
Only effusion0002
No synovitis or effusion341138

Table 4 presents the results of the power Doppler US examination and the clinical assessment of the inflammatory activity in the joints, grouped similarly to that of the B-mode US results. Power Doppler signal in the synovium was present in 43 joints, of which 26 (60%) showed clinical signs of inflammation (swelling and/or tenderness). Power Doppler signal in the synovium was absent in 107 joints, of which 38 (36%) presented clinical signs of inflammation.

Table 4. Clinical joint assessment performed on 150 small joints of 30 rheumatoid arthritis patients by an experienced rheumatologist versus power Doppler examination by an observer with a short training period*
Power Doppler assessmentClinical assessment
Swelling and tendernessOnly swellingOnly tendernessNo swelling or tenderness
  • *

    Values are the no. of joints with the examined parameter.

Signal present125917
Signal absent1681469

DISCUSSION

  1. Top of page
  2. Abstract
  3. PATIENTS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

There is accumulating evidence of the usefulness of US for the diagnosis and monitoring of different rheumatic disorders (1). US units of sufficient quality for examination of the small joints of the extremities have become increasingly available, and the interest in ultrasonography among rheumatologists is growing. Yet, US for assessment of arthritis in the small joints is poorly validated in comparison with its many other applications (10–12).

Because operator dependence is considered to be one of the major disadvantages of musculoskeletal US (4, 5), we decided to investigate the interobserver agreement for 4 important parameters in the US assessment of RA in hand and foot joints. Due to the ordinal character of the data in the study, the ICC was considered the primary outcome measure. The unweighted kappa and overall agreement, which only assess presence or absence of absolute agreement, were also calculated. The present study introduced a semiquantitative scoring system for joint effusion, synovitis, bone erosions, and power Doppler signal in the small joints of the extremities, which is illustrated in Figures 1–4.

Assessment of synovitis and bone erosions showed a good interobserver agreement (ICC 0.78–0.81, unweighted kappa 0.63–0.68). Agreements on the assessment of joint effusion and power Doppler signal were moderate to good (ICC 0.61–0.72, unweighted kappa 0.48–0.55). (Table 1). These interobserver agreement values are not inferior to the corresponding values for other methods of assessment of RA joint disease (13). Agreements varied from joint to joint probably reflecting the anatomic localization and availability for examination. The third MCP joint, which is difficult to access by US, showed relatively low agreement rates compared with the easily accessed second MCP joint. However, the second MTP joint, anatomically equally as difficult to access as the third MCP joint, showed markedly better agreement rates, possibly due to fewer variations in the US examination of the joint. Our data are in accordance with the observations by Wakefield et al (14), who reported interobserver agreements (kappa values) for RA bone erosions of 0.76 versus 0.68 in the present study. No other studies, to our knowledge, have examined interobserver variation in the assessment of the remaining parameters in this study.

Different backgrounds and experience of the US investigators did not markedly influence the results, as shown by Bland-Altman plots (Figure 5), which revealed no systematic difference between the investigators. This suggests that with suitable training, a rheumatologist can satisfactorily perform ultrasonography on finger and toe joints with RA. In comparison with clinical assessment of the small joints, US showed many more joints with signs assumed to reflect inflammation (US 94 joints versus clinical 64 joints). Furthermore, there were very few false negative results by US (12%), but the etiology in those joints remained unknown. If the additional information obtained by US is shown to be of clinical significance in longitudinal studies, US may take an important place in the assessment of the RA joints.

As previously described (9), power Doppler flow signal is not frequently detected in small joints with RA. In the present study, power Doppler signal in the synovial membrane was present in 43 of 94 joints which showed signs of inflammation on B-mode US (joint effusion and synovial thickening). With the high-end US equipment now available, or by using US contrast agents (8, 15), more joints may be visualized with power Doppler signal.

In conclusion, this study suggests that ultrasonography is a reproducible method for assessment of inflammatory and destructive changes in the finger and toe joints of patients with RA. After suitable training, this technique can be used by rheumatologists for improved assessment of RA patients. Furthermore, the study introduces a semiquantitative scoring system for the examined parameters.

Acknowledgements

  1. Top of page
  2. Abstract
  3. PATIENTS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

We thank Ms Susanne Østergaard and Ms Zofia Kruszona for their assistance with the medical illustrations.

REFERENCES

  1. Top of page
  2. Abstract
  3. PATIENTS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES
  • 1
    McGonagle D, Conaghan PG, Wakefield R, Emery P. Imaging the joints in early rheumatoid arthritis. Best Pract Res Clin Rheumatol 2001; 15: 91104.
  • 2
    Backhaus M, Kamradt T, Sandrock D, Loreck D, Fritz J, Wolf KJ, et al. Arthritis of the finger joints: a comprehensive approach comparing conventional radiography, scintigraphy, ultrasound, and contrast-enhanced magnetic resonance imaging. Arthritis Rheum 1999; 42: 123245.
  • 3
    Jacobson JA, Andresen R, Jaovisidha S, De Maeseneer M, Foldes K, Trudell DR, et al. Detection of ankle effusions: comparison study in cadavers using radiography, sonography, and MR imaging. Am J Roentgenol 1998; 170: 12318.
  • 4
    Balint PV, Sturrock RD. Intraobserver repeatability and interobserver reproducibility in musculoskeletal ultrasound imaging measurements. Clin Exp Rheumatol 2001; 19: 8992.
  • 5
    Zanetti M, Hodler J. Sonography of the musculoskeletal system. Ther Umsch 1997; 54: 1823.
  • 6
    Van der Heijde DM. Radiographic imaging: the “gold standard” for assessment of disease progression in rheumatoid arthritis. Rheumatology (Oxford) 2000; 39 Suppl 1: 916.
  • 7
    Arnett FC, Edworthy SM, Bloch DA, McShane DJ, Fries JF, Cooper NS, et al. The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis. Arthritis Rheum 1988; 31: 31524.
  • 8
    Szkudlarek M, Court-Payen M, Strandberg C, Klarlund M, Klausen T, Østergaard M. Contrast-enhanced power Doppler ultrasonography of the metacarpophalangeal joints in rheumatoid arthritis. Eur Radiol 2003; 13: 1638.
  • 9
    Szkudlarek M, Court-Payen M, Strandberg C, Klarlund M, Klausen T, Østergaard M. Power Doppler ultrasonography for assessment of synovitis in the metacarpophalangeal joints of patients with rheumatoid arthritis: a comparison with dynamic magnetic resonance imaging. Arthritis Rheum 2001; 44: 201823.
  • 10
    Baker JA, Kornguth PJ, Soo MS, Walsh R, Mengoni P. Sonography of solid breast lesions: observer variability of lesion description and assessment. Am J Roentgenol 1999; 172: 16215.
  • 11
    Burtin P, Rabot AF, Heresbach D, Carpentier S, Rousselet MC, Le Berre N, et al. Interobserver agreement in the staging of rectal cancer using endoscopic ultrasonography. Endoscopy 1997; 29: 6205.
  • 12
    Dick PT, Shuckett BM, Tang B, Daneman A, Kooh SW. Observer reliability in grading nephrocalcinosis on ultrasound examinations in children. Pediatr Radiol 1999; 29: 6872.
  • 13
    Lassere MND, van der Heijde D, Johnson KR, Boers M, Edmonds J. Reliability of measures of disease activity and disease damage in rheumatoid arthritis: implications for smallest detectable difference, minimal clinically important difference, and analysis of treatment effects in randomized controlled trials. J Rheumatol 2001; 28: 892903.
  • 14
    Wakefield RJ, Gibbon WW, Conaghan PG, O'Connor P, McGonagle D, Pease C, et al. The value of sonography in the detection of bone erosions in patients with rheumatoid arthritis: a comparison with conventional radiography. Arthritis Rheum 2000; 43: 276270.
  • 15
    Klauser A, Frauscher F, Schirmer M, Halpern E, Pallwein L, Herold M, et al. The value of contrast-enhanced color Doppler ultrasound in the detection of vascularization of finger joints in patients with rheumatoid arthritis. Arthritis Rheum 2001; 46: 64753.