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Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Objective

To analyze the diagnostic performance and reliability of different parameters evaluated by widefield nailfold capillaroscopy (NFC) with those obtained by videocapillaroscopy in patients with Raynaud's phenomenon (RP).

Methods

Two hundred fifty-two individuals were assessed, including 101 systemic sclerosis (SSc; scleroderma) patients, 61 patients with undifferentiated connective tissue disease, 37 patients with primary RP, and 53 controls. Widefield NFC was performed using a stereomicroscope under 10–25× magnification and direct measurement of all parameters. Videocapillaroscopy was performed under 200× magnification, with the acquirement of 32 images per individual (4 fields per finger in 8 fingers). The following parameters were analyzed in 8 fingers of the hands (excluding thumbs) by both methods: number of capillaries/mm, number of enlarged and giant capillaries, microhemorrhages, and avascular score. Intra- and interobserver reliability was evaluated by performing both examinations in 20 individuals on 2 different days and by 2 long-term experienced observers.

Results

There was a significant correlation (P < 0.000) between widefield NFC and videocapillaroscopy in the comparison of all parameters. Kappa values and intraclass correlation coefficient analysis showed excellent intra- and interobserver reproducibility for all parameters evaluated by widefield NFC and videocapillaroscopy. Bland-Altman analysis showed high agreement of all parameters evaluated in both methods. According to receiver operating characteristic curve analysis, both methods showed a similar performance in discriminating SSc patients from controls.

Conclusion

Widefield NFC and videocapillaroscopy are reliable and accurate methods and can be used equally for assessing peripheral microangiopathy in RP and SSc patients. Nonetheless, the high reliability obtained may not be similar for less experienced examiners.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Nailfold capillaroscopy (NFC) is a well-established method that allows the assessment of microcirculation in patients with Raynaud's phenomenon (RP). It is extremely useful for differential diagnosis between primary and secondary RP and for early diagnosis of systemic sclerosis (SSc; scleroderma). Patients with SSc and scleroderma spectrum disorders exhibit a typical pattern at NFC designated “scleroderma pattern,” and characterized by enlarged capillary loops, loss of capillaries, areas of hemorrhages, disruption of the orderly appearance of the capillary bed, and distortion of capillaries ([1]). These abnormalities can be recognized in early stages of SSc, even when clinical features of the disease are only limited to RP ([2]). In addition, an improvement in the microangiopathic abnormalities characteristic of the scleroderma pattern was described after autologous hemopoietic stem cell transplantation in patients with severe SSc, suggesting a possible role of NFC for therapy monitoring as well ([3]).

There are several methods and pieces of equipment for performing capillaroscopy, including the stereomicroscope, dermatoscope, ophthalmoscope, and videocapillaroscope. According to previous studies, dermatoscopes and ophthalmoscopes offer lower performances compared to stereomicroscopy and videomicroscopy ([4, 5]). Widefield NFC is a simple and low-cost method largely studied by Maricq et al 30–40 years ago. It is traditionally performed with a stereomicroscope at 10–40× magnification, allowing a global overview of the entire capillary network at the nailfold region ([1]). By widefield NFC, capillary loops are evaluated using qualitative and semiquantitative approaches, as well as by means of quantitative measurement of the capillary density ([6]). The videocapillaroscopy system is an extension of the panoramic capillaroscopy in which the magnification used is much higher (200–600× magnification) than the widefield technique ([7]). Videocapillaroscopes are equipped with specific software that allows detailed measurement of specific parameters such as the dimensions of individual capillary loops, as well as the afferent and efferent luminal diameters ([8, 9]). However, only a restricted part of the nailfold region is assessed at a time, due to the high magnification power used in this technique.

Despite the increasing interest in NFC and its remarkable utility in clinical practice and research, there is no consensus or standardized approach to the evaluation of several capillaroscopic parameters. Recent studies have been published evaluating the reliability of videocapillaroscopy ([7, 10-12]), but studies comparing the performance of widefield NFC and videocapillaroscopy are scarce ([13, 14]). The present study aimed to evaluate and compare the diagnostic performance and reliability of different parameters evaluated by widefield NFC with those obtained by videocapillaroscopy in the assessment of microcirculation in patients with several forms of RP.

Box 1. Significance & Innovations

  • Nailfold capillaroscopy (NFC) is an important tool for the investigation of patients with Raynaud's phenomenon (RP). Nevertheless, there is no guideline about the method and the parameters that should be evaluated.
  • The performance for the diagnosis of systemic sclerosis (SSc) and the reliability of widefield NFC, a simple and low-cost method, were compared with those obtained by videocapillaroscopy, which is considered a more sophisticated method.
  • Widefield NFC and videocapillaroscopy showed a similar performance in discriminating SSc patients from controls and RP patients. There was excellent intra- and interobserver agreement for all parameters evaluated by both methods.
  • Widefield NFC and videocapillaroscopy were reliable methods, suggesting that both can be used equally for assessing peripheral microangiopathy in RP and SSc patients.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Patients

Two hundred fifty-two individuals were consecutively included in this cross-sectional study according to the following groups: 1) 101 patients with an SSc diagnosis according to the American College of Rheumatology classification criteria (mean ± SD age 50.0 ± 14.5 years, 10 men and 91 women) ([15]); 2) 61 patients with RP associated with undifferentiated connective tissue disease (UCTD; mean ± SD age 44.4 ± 15.5 years, 4 men and 57 women); this group of patients manifested with signs of CTD, but did not fit the accepted classification criteria for SSc, systemic lupus erythematosus, or other definite CTD; 3) 37 patients with primary RP (mean ± SD age 40.6 ± 15.6 years, 2 men and 35 women) defined according to the 1992 criteria by LeRoy and Medsger ([16]); and 4) 53 healthy controls (mean ± SD age 48.9 ± 14.3 years, 9 men and 44 women), composed of students and hospital employees at Universidade Federal de São Paulo (UNIFESP) Medical School Hospital.

All SSc patients were selected from the Scleroderma Outpatient Clinic at UNIFESP Medical School Hospital. Patients with UCTD and primary RP were selected from the Scleroderma Outpatient Clinic or from primary care units. Patients with SSc with severe flexion contracture of the hands or overlapping with systemic lupus erythematosus, rheumatoid arthritis, or polymyositis/dermatomyositis were excluded. The study was approved by the UNIFESP Ethics Committee, and all individuals filled out an informed consent form.

All individuals underwent a thorough rheumatologic examination, and information about RP duration and duration of the disease was recorded for all patients. Antinuclear antibodies (ANAs) were determined by indirect immunofluorescence using HEp-2 cells as a substrate in all patients. Anticentromere antibodies (ACAs) were identified by the typical pattern on the indirect immunofluorescence HEp-2 cell assay and anti–topoisomerase I (anti–Scl-70) antibodies were determined by the double immunodiffusion method against rabbit thymus extract.

NFC

After acclimatization during 60 minutes in a laboratory with a stable mean ± SD temperature of 24°C ± 1°C, all individuals underwent widefield NFC and videocapillaroscopy on the same day. All procedures were performed by the same observer (JYS), who was blinded to the patients' clinical conditions and laboratory data. Widefield NFC was performed by direct counting and measurement of each parameter. Videocapillaroscopy analyses were performed on coded images. The 8 fingers of the hands (excluding thumbs) were examined in both procedures, except when prevented by extremely poor visibility due to active ulcers around the fingertip or amputation.

Widefield NFC procedures were performed using a stereomicroscope (SZ40, Olympus) under 10–25× magnification according to the protocol proposed by Andrade et al ([6]). A transparent ruler incorporated to the right eyepiece of the stereomicroscope allowed reproducible measurement of the capillary width and of the number of capillary loops per millimeter. The following parameters were determined: the number of capillary loops/mm, the number of microhemorrhages, the number of enlarged loops (>4 times the normal afferent, transition, and efferent limb width), the number of giant capillary loops (≥10 times the normal width of capillary limbs), and the avascular score ([17]). The avascular score was assessed according to the method by Lee and colleagues ([18]), in which a deletion area is defined as the absence of ≥2 consecutive loops. Each finger was rated from 0–3, where 0 = no deletion area, 1 = 1 or 2 discrete deletion areas, 2 = >2 discrete deletion areas, and 3 = extensive and confluent deletion areas. For each patient, the NFC parameters were calculated based upon the average obtained in all analyzed fingers.

Videocapillaroscopy was performed using an optical videocapillaroscopic probe under a contact lens at 200× magnification and connected to image analysis software (Videocap 8.14, DS-Medica). Four consecutive fields per finger were studied as described previously ([19]). All images were stored and made anonymous before being evaluated. The following parameters were scored over the 32 fields (4 fields per finger in 8 fingers): number of capillaries/mm, number of enlarged capillaries (homogeneously or irregular enlarged loops with a diameter >20 μm), number of giant capillaries (homogeneously enlarged loops with a diameter >50 μm), and number of microhemorrhages (dark mass due to hemosiderin deposit). For the measurement of capillary loss (avascular score), the normal value of 9 capillaries/mm was adopted ([6, 19]). For each parameter, a semiquantitative rating scale (range 0–3, where 0 = no changes, 1 = <33% of capillary changes or reduction, 2 = 33–66% of capillary changes or reduction, and 3 = >66% of capillary changes or reduction per linear mm) was adopted according to previous studies ([2, 19]). The mean score value for each capillaroscopic parameter was calculated from the analysis of the 4 consecutive fields in each finger. The mean scores from the 8 fingers were added together and the final value was divided by the total number of fingers evaluated ([19]).

All patients and controls were also classified according 3 different patterns found on widefield NFC and videocapillaroscopy: normal pattern, nonspecific microangiopathy, and scleroderma pattern.

Intra- and interobserver reliability

Intra- and interobserver reliability was evaluated by performing each examination in 20 individuals on 2 different days and by 2 different observers (JYS, CZC). The maximum time interval between the 2 evaluations performed by the same observer was 4 weeks.

Statistical analysis

Results are expressed as the mean ± SD. The Kolmogorov-Smirnov test was used to evaluate normality distribution. Comparison between groups was performed using the Kruskal-Wallis test for continuous variables and the chi-square test or Fisher's exact test for categorical data. Spearman's correlation method was used to evaluate the correlation between the capillaroscopic parameters evaluated by widefield NFC and videocapillaroscopy. Statistical analysis was performed using SPSS statistical software, version 17.0. A P value less than 0.05 was considered significant.

The performance of widefield NFC and videocapillaroscopy in discriminating SSc patients from controls and patients with RP (primary RP and UCTD) was compared by means of receiver operating characteristic (ROC) curve analysis. Two parameters were evaluated: number of capillaries/mm and the avascular score. The values of the area under the curve (AUC) were interpreted as 0.91–1 = excellent, 0.81–0.90 = good, 0.71–0.80 = fair, 0.61–0.70 = poor, and 0.50–0.60 = failure. The best cutoff values for the number of capillaries/mm and for the avascular score were calculated based on the Youden index criteria (the value for which the maximum difference between sensitivity and 1 − specificity is attained) ([20]).

Intra- and interobserver reliability for assessment of all capillaroscopy parameters was analyzed using the intraclass correlation coefficient (ICC) and the Bland-Altman approach ([21]). The reliability of capillaroscopy patterns (normal pattern, nonspecific microangiopathy, and scleroderma pattern) was analyzed using weighted kappa. The kappa values were interpreted using the following guidelines: 0–0.20 = poor, 0.21–0.40 = fair, 0.41–0.60 = moderate, 0.61–0.80 = good, and 0.81–1 = almost perfect (excellent) ([22]).

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Demographic and clinical characteristics of the cohort

Of the 252 individuals, 227 (90%) were women and 25 were men. The mean age of the primary RP patients was significantly lower compared to the controls (P = 0.048) and SSc patients (P = 0.006). Positive ANA was found in 91% of patients with SSc, 75% of patients with UCTD, and 24% of patients with primary RP (titer lower than 1:160). Anti–Scl-70 antibodies were positive only in SSc patients (9%). ACA was present in 30% of SSc patients and 28% of UCTD patients. The mean ± SD RP duration was 6.7 ± 5.3 years in primary RP patients, 8.6 ± 9.1 years in UCTD patients, and 9.7 ± 9.0 years in SSc patients (P = 0.167). The mean ± SD disease duration was 5.2 ± 7.9 years in UCTD patients and 7.5 ± 6.5 years in SSc patients (P = 0.042). Thirty-two SSc patients were classified as having diffuse cutaneous SSc and 69 were classified as having limited cutaneous SSc.

Widefield NFC and videocapillaroscopy parameters

A total of 8,064 images were analyzed by videocapillaroscopy (32 images per individual in 252 individuals). Widefield NFC was performed without image capture, with real-time evaluation of the entire nailfold region of each finger and direct measurement of all parameters. In both methods, SSc patients showed significantly lower numbers of capillaries/mm and significantly higher numbers of enlarged and giant capillaries, numbers of microhemorrhages, and avascular scores compared to controls and patients with primary RP and UCTD (Table 1). There was a significant correlation (P < 0.000) between widefield NFC and videocapillaroscopy in the comparison of all evaluated parameters (number of capillaries/mm, r = 0.874; enlarged capillaries, r = 0.902; giant capillaries, r = 0.882; microhemorrhages, r = 0.601; and avascular score, r = 0.814).

Table 1. Widefield NFC and videocapillaroscopy parameters in patients with primary RP, UCTD, and SSc and in healthy controls*
 Controls (n = 53)Primary RP (n = 37)UCTD (n = 61)SSc (n = 101)P
  1. Values are the mean ± SD. NFC = nailfold capillaroscopy; RP = Raynaud's phenomenon; UCTD = undifferentiated connective tissue disease; SSc = systemic sclerosis.

  2. a

    Controls versus SSc and primary RP versus SSc: P < 0.001. Controls versus primary RP and UCTD versus SSc: P < 0.01.

  3. b

    Controls versus SSc and primary RP versus SSc: P < 0.001.

  4. c

    Controls versus primary RP and UCTD versus SSc: P < 0.01. Controls versus UCTD and primary RP versus UCTD: P < 0.05.

  5. d

    Controls versus SSc and primary RP versus SSc: P < 0.001. Controls versus UCTD and primary RP versus UCTD: P < 0.05.

  6. e

    Controls versus primary RP and UCTD versus SSc: P < 0.01.

Widefield NFC     
Number of capillary loops/mm10.05 ± 0.46a9.72 ± 0.63b9.68 ± 0.61c7.96 ± 1.57< 0.001
Number of enlarged capillary loops0.005 ± 0.02a0.23 ± 0.28d0.84 ± 0.96c3.09 ± 2.48< 0.001
Number of giant capillary loops0.00 ± 0.01b0d0.03 ± 0.11c0.78 ± 1.17< 0.001
Number of microhemorrhages0.01 ± 0.08b0.05 ± 0.23b0.07 ± 0.26c0.77 ± 1.29< 0.001
Avascular score (range 0–3)0b0d0.12 ± 0.26c1.27 ± 0.98< 0.001
Videocapillaroscopy     
Number of capillary loops/mm10.10 ± 0.56b10.04 ± 1.15b9.65 ± 0.86c7.71 ± 1.70< 0.001
Enlarged capillary score (range 0–3)0.007 ± 0.01a0.06 ± 0.10d0.22 ± 0.26c0.70 ± 0.48< 0.001
Giant capillary score (range 0–3)0 ± 0.004b0.001 ± 0.006b0.01 ± 0.05e0.17 ± 0.28< 0.001
Microhemorrhage score (range 0–3)0.002 ± 0.009b0.009 ± 0.02d0.03 ± 0.08c0.13 ± 0.00< 0.001
Avascular score (range 0–3)0.19 ± 0.24b0.38 ± 0.37b0.37 ± 0.39c1.12 ± 0.55< 0.001

A normal pattern was found in 98% of the controls in both methods and in 84% and 87% of primary RP patients by widefield NFC and videocapillaroscopy, respectively. Nonspecific microangiopathy prevailed in patients with UCTD (31% by widefield NFC and 29% by videocapillaroscopy) and in patients with primary RP (16% by widefield NFC and 13% by videocapillaroscopy). The typical scleroderma pattern was found only in patients with SSc (91% by widefield NFC and 83% by videocapillaroscopy) or UCTD (28% by widefield NFC and 20% by videocapillaroscopy).

Diagnostic performance of widefield NFC and videocapillaroscopy

A mean number of capillaries/mm of 9.1 and 9.0 and a mean avascular score of 0.05 and 0.5 were chosen as the cutoff values for SSc diagnosis using widefield NFC and videocapillaroscopy, respectively. According to Table 2, both parameters and both methods yielded high sensitivity and specificity as well as good positive and negative predictive values for the diagnosis of SSc.

Table 2. Sensitivity, specificity, PPV, and NPV of widefield NFC and videocapillaroscopy methods for the diagnosis of systemic sclerosis*
 Cutoff valueSensitivity, %Specificity, %PPV, %NPV, %
  1. PPV = positive predictive value; NPV = negative predictive value; NFC = nailfold capillaroscopy.

Number of capillaries/mm     
Widefield NFC≤9.172949664
Videocapillaroscopy≤9.07210010065
Avascular score     
Widefield NFC≥0.059110010091
Videocapillaroscopy≥0.5086949778

According to ROC curve analysis, widefield NFC and videocapillaroscopy showed a similar performance in discriminating SSc patients from healthy controls (Figure 1). ROC curve analyses for the number of capillaries/mm showed AUCs of 0.906 (P < 0.001, 95% confidence interval [95% CI] 0.859–0.954) using the widefield NFC method and 0.935 (P < 0.001, 95% CI 0.895–0.975) using videocapillaroscopy (Figure 1A). The ROC curve analyses for the avascular score showed AUCs of 0.955 (P < 0.001, 95% CI 0.922–0.989) using widefield NFC and 0.947 (P < 0.001, 95% CI 0.913–0.982) using videocapillaroscopy (Figure 1B). The diagnostic performance of both methods in discriminating SSc patients from the 151 non-SSc patients (healthy controls, primary RP patients, and UCTD patients) was also evaluated. ROC curve analyses for the number of capillaries/mm showed AUCs of 0.858 (P < 0.001, 95% CI 0.806–0.909) using the widefield NFC method and 0.894 (P < 0.001, 95% CI 0.850–0.938) using videocapillaroscopy. For the avascular score, the AUCs were 0.929 (P < 0.001, 95% CI 0.892–0.966) using widefield NFC and 0.947 (P < 0.001, 95% CI 0.858–0.934) using videocapillaroscopy. There was also a good diagnostic performance of widefield NFC and videocapillaroscopy for SSc diagnosis compared only to patients with UCTD and primary RP. The ROC curve analysis for the number of capillaries/mm showed AUCs of 0.831 (P < 0.000, 95% CI 0.774–0.889) using widefield NFC and 0.872 using videocapillaroscopy (P < 0.000, 95% CI 0.821–0.922). For the avascular score, the AUCs were 0.915 (P < 0.000, 95% CI 0.874–0.956) using widefield NFC and 0.869 (P < 0.000, 95% CI 0.821–0.916) using videocapillaroscopy. When evaluating only SSc patients with <4 years of disease versus primary RP and UCTD patients, the ROC curve analysis for the number of capillaries/mm showed AUCs of 0.851 (P < 0.000, 95% CI 0.764–0.938) using widefield NFC and 0.926 using videocapillaroscopy (P < 0.000, 95% CI 0.872–0.980). For the avascular score, the AUCs were 0.954 (P < 0.000, 95% CI 0.906–1.0) using widefield NFC and 0.909 (P < 0.000, 95% CI 0.855–0.963) using videocapillaroscopy.

image

Figure 1. Receiver operating characteristic curves for discriminating systemic sclerosis patients from controls using the parameters number of capillaries/mm (A) and avascular score (B) evaluated with widefield nailfold capillaroscopy (NFC) and videocapillaroscopy.

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Reliability of widefield NFC and videocapillaroscopy

Assessment of the 3 different capillaroscopy patterns (normal pattern, nonspecific microangiopathy, and scleroderma pattern) by means of widefield NFC showed almost perfect interobserver and intraobserver agreement (κ = 1, P < 0.001 for both intra- and interobserver assessments). Videocapillaroscopy also showed almost perfect intraobserver (κ = 1, P < 0.001) and interobserver (κ = 0.917, P < 0.001) agreement. The ICC analysis showed an excellent intra- and interobserver ICC for all parameters evaluated by widefield NFC as well as for all parameters evaluated by videocapillaroscopy (Table 3). Bland-Altman analysis for intraobserver repeatability and interobserver reproducibility showed high agreement of all parameters evaluated in both methods (data from enlarged and giant capillaries and microhemorrhages are not shown) (Figures 2 and 3). As observed in all plots, the differences between the 2 measurements are mostly found within the upper limit and lower limit of agreement, and with a low bias.

Table 3. ICCs for intra- and interobserver reliability of different parameters evaluated by widefield NFC and videocapillaroscopy*
 Intraobserver reliabilityInterobserver reliability
ICC95% CIICC95% CI
  1. ICC = intraclass correlation coefficient; NFC = nailfold capillaroscopy; 95% CI = 95% confidence interval.

Widefield NFC    
Number of capillaries/mm0.9930.983–0.9970.9540.884–0.981
Enlarged capillary loops0.9980.996–0.9990.9520.883–0.981
Giant capillary loops0.9940.985–0.9980.9930.982–0.997
Microhemorrhages0.9460.869–0.9780.9930.982–0.997
Avascular score0.9980.996–0.9990.9980.994–0.999
Videocapillaroscopy    
Number of capillaries/mm0.9910.976–0.9960.9520.883–0.981
Enlarged capillary loops0.9990.998–1.0000.9640.912–0.986
Giant capillary loops0.9990.997–1.0000.9950.987–0.998
Microhemorrhages0.9650.914–0.9860.8980.761–0.958
Avascular score0.9980.996–0.9990.9850.963–0.994
image

Figure 2. Bland-Altman plots showing interobserver agreement of the number of capillaries/mm and avascular score for widefield nailfold capillaroscopy (A and B, respectively) and videocapillaroscopy (C and D, respectively). Broken lines show the mean of the percentage change and dotted lines define the limits of agreement (SD of the percentage of change × 1.96 SDs).

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image

Figure 3. Bland-Altman plots showing intraobserver agreement of the number of capillaries/mm and avascular score for widefield nailfold capillaroscopy (A and B, respectively) and videocapillaroscopy (C and D, respectively). Broken lines show the mean of the percentage change and dotted lines define the limits of agreement (SD of the percentage of change × 1.96 SDs).

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DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

NFC is considered one of the most important tools for the evaluation of microcirculation and early diagnosis of SSc. The present study originally performed a head-to-head comparison between 2 NFC methods (widefield NFC and videocapillaroscopy) that are widely used in clinical practice and research. The most important parameters related to the scleroderma pattern were analyzed by both methods. Both widefield NFC and videocapillaroscopy were equally able to discriminate SSc patients from healthy controls and from non-SSc patients with RP. The comparison between widefield NFC and videocapillaroscopy showed a strong and significant correlation in the evaluation of the number of capillaries/mm, enlarged capillaries, giant capillaries, and avascular areas. Finally, there was excellent intra- and interobserver reliability for all parameters evaluated either by widefield NFC or by videocapillaroscopy.

Widefield NFC is considered a classic approach based on the use of optical instruments (i.e., stereomicroscope) under low magnification. The advantage of this method is the panoramic view of the entire nailfold microvascular network, allowing the prompt identification of specific panoramic microangiopathic patterns and localization of isolated morphologic abnormalities ([6, 8]). Widefield NFC also has the advantage of being a lower-cost method, making it suitable for clinical use in smaller centers. On the other hand, it has been considered a more subjective method, with some limitations regarding reproducibility, especially when quantitative evaluation of the microangiopathy is required ([2, 23]). This could be explained by the fact that early widefield NFC descriptions were purely subjective and based only on specific pattern recognition. To reduce this limitation, several quantitative and semiquantitative techniques have been developed ([6]).

Videocapillaroscopy is considered to be the most sophisticated method for nailfold capillary examination at present ([24]). Due to special digital systems, this technique has been considered highly reliable and user friendly ([2]). Because images are recorded and stored, it is possible to perform blind analysis of the data and to follow individual capillaries in the same patient, allowing the quantitation of microvascular disease progression over time, making this a great advantage in longitudinal studies and research. A limitation of this method is represented by the fact that the application of even minimal pressure to the skin by the probe can reduce or interrupt the blood flow in the capillaries and consequently impair the evaluation of the capillary loops along the nailfold margin ([6, 23]). In addition, the acquisition and posterior analysis of each image (32 images per patient) is extremely laborious and more time consuming compared to the widefield NFC method.

Although the sensitivity and specificity of NFC in the diagnosis of SSc have already been evaluated in previous studies ([13, 25]), this was the first study to perform a comparison of the sensitivity and specificity of different parameters as assessed by widefield NFC versus videocapillaroscopy in the same individuals. The most frequent parameters used in other studies, such as the number of capillaries/mm and devascularization ([9, 11, 26]), were evaluated. Both the avascular score and the number of capillaries/mm showed high sensitivity and specificity for SSc diagnosis using either videocapillaroscopy or widefield NFC. As expected, the performance of both methods was slightly higher when only healthy controls were compared to SSc patients, with excellent areas under the curve for both parameters analyzed (number of capillaries/mm and avascular score). However, when comparing SSc patients with the other 3 groups (controls and primary RP and UCTD patients), ROC curve analysis also showed an excellent AUC for the avascular score. In addition, the analyses of SSc patients with less than 4 years of disease showed a similar diagnostic performance, confirming the importance of the method for early diagnosis of the disease.

In a more synthetic approach, the most relevant NFC patterns were also evaluated by widefield NFC and videocapillaroscopy, again showing a similar diagnostic performance. An interesting finding was the presence of scleroderma pattern in 20–28% of the UCTD patients. These patients could also be classified as having early SSc according to the LeRoy and Medsger criteria from 2001 ([27]), and are already being followed for monitoring of disease progression due to the high risk of developing SSc ([19, 28]).

An important aspect evaluated in the present study was the interobserver reproducibility and the intraobserver repeatability of both methods. Parameters with poor agreement in previous studies such as meandering, tortuous and bizarre capillaries, skin transparency, and intercapillary distance measurements were not evaluated ([29, 30]). The weighted kappa values showed excellent interobserver and intraobserver agreement on both methods, showing that both widefield NFC and videocapillaroscopy are highly reliable for the evaluation of different capillaroscopy patterns. Recently, Gutierrez et al (2012) evaluated the learning curve of rheumatologists with different background experience in videocapillaroscopy by means of a 1-week intensive training program focused on the interpretation of the main capillary nailfold abnormalities, including the normal and scleroderma patterns ([12]). There was a progressive improvement in the interreader agreement from the beginning to the end of the training program. Nonetheless, we believe that more extensive training is necessary to deepen the knowledge of the wide range of normal findings as well as for research studies. In our study, the almost perfect agreement obtained can be explained by the long-term experience of both observers with NFC, and may not be similar for less experienced observers.

ICCs also showed high agreement in all parameters (number of capillaries/mm, enlarged capillaries, giant capillaries, microhemorrhages, and avascular score) evaluated by both methods. Recently, Wildt et al (2012) evaluated the capillary density (number of loops/mm) using a stereomicroscope and a videocapillaroscope in 40 patients with SSc and 21 controls. There was a good agreement rate between the methods, confirming the results found in the present study ([13]). Moreover, 2 other studies evaluated inter- and intraobserver reliability of videocapillaroscopy only. Smith et al (2010) evaluated the inter- and intraobserver reliability of qualitative and 4 semiquantitative parameters (capillary loss, giant capillaries, microhemorrhages, and capillary ramifications) between 2 observers from 2 different centers in 71 SSc patients ([11]). The inter- and intraobserver agreement rates for the semiquantitative scoring showed similar results compared to the present study. Another study found almost perfect inter- and intraobserver agreement for identification of major abnormalities (including giant capillaries) and good inter- and intraobserver agreement regarding analysis of the number of capillaries/mm, avascularity, and hemorrhages ([10]). There was also good agreement in the evaluation of capillary disorganization, which was not evaluated in our study. Finally, Bland-Altman analysis also showed high agreement rates for all parameters evaluated by widefield NFC and videocapillaroscopy in the present study.

The present findings of high agreement rates for capillaroscopic parameters assessed by both methods suggest that, although widefield NFC measurements can be considered more subjective compared to videocapillaroscopy systems, both methods can be used in clinical practice in an accurate and reliable fashion. Nonetheless, it should be noted that the examinations were performed by 2 investigators from a single center and with long-term experience in widefield NFC. Therefore, we cannot extrapolate that such a good widefield NFC performance will be achieved in a scenario in which the investigators have modest experience with the method. Moreover, due to the high quality of the images, videocapillaroscopy can be more suitable for longitudinal followup and research ([31]).

In conclusion, several recent studies have highlighted the importance of NFC for the investigation of patients with RP ([32-34]). In fact, NFC was included among the criteria for early diagnosis of SSc ([27]), underlining the importance of the method for the identification of patients with SSc. In the present study, both widefield NFC and videocapillaroscopy were shown to be able to differentiate SSc patients from controls and patients with RP. Moreover, both methods showed excellent reliability, suggesting that both approaches can be used equally for assessing peripheral microangiopathy in RP and SSc patients. However, due to the operator-dependent characteristic of both methods, further multicenter and longitudinal studies are warranted in order to expand the present findings to other investigators in the clinical and research scenarios.

AUTHOR CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. Dr. Kayser had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study conception and design. Sekiyama, Camargo, Andrade, Kayser.

Acquisition of data. Sekiyama, Camargo, Andrade, Kayser.

Analysis and interpretation of data. Kayser.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES
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