Symptoms of Raynaud's phenomenon (RP) in fibromyalgia syndrome are similar to those reported in primary RP despite differences in objective assessment of digital microvascular function and morphology.

Symptoms of Raynaud's phenomenon (RP) are common in fibromyalgia syndrome (FMS). We compared symptom characteristics and objective assessment of digital microvascular function using infrared thermography (and nailfold capillaroscopy where available) in patients with FMS (reporting RP symptoms) and primary RP. We retrospectively reviewed the outcome of microvascular imaging studies and RP symptom characteristics (captured using patient-completed questionnaire at the time of assessment) for patients with FMS (reporting RP symptoms) and patients with primary RP referred for thermographic assessment of RP symptoms over a 2-year period. Of 257 patients referred for thermographic assessment of RP symptoms between 2010 and 2012, we identified 85 patients with primary RP and 43 patients with FMS. There were no differences in RP symptom characteristics between FMS and primary RP (p > 0.05 for all comparisons). In contrast, patients with FMS had higher baseline temperature of the digits (32.1 vs. 29.0 °C, p = 0.004), dorsum (31.9 vs. 30.2 °C, p = 0.005) and thermal gradient (temperature of digits minus temperature of dorsum; +0.0 vs. -0.9 °C, p = 0.03) compared with primary RP. Significant differences between groups persisted following local cold challenge. In primary RP, patient reporting "blue" digits, bi-phasic and tri-phasic RP was associated with lower digital perfusion. In contrast, no associations between skin temperature and RP digital colour changes/phases were identified in FMS. Our findings suggest that symptoms of RP in FMS may have a different aetiology to those seen in primary RP. These findings have potential implications for both the classification of RP symptoms and the management of RP symptoms in the context of FMS. Digital colour changes reported by patients might reflect the degree of digital microvascular compromise in primary RP.

Comparison of infrared thermography and laser speckle contrast imaging for the dynamic assessment of digital microvascular function.

OBJECTIVES: Laser speckle contrast imaging (LSCI) is a novel non-invasive microvascular imaging modality. The present study evaluates the validity and reliability of LSCI by comparison with infrared thermography (IRT) for the dynamic assessment of digital microvascular function in healthy volunteers. METHODS: Subjects attended on 3 occasions. Simultaneous assessment of cutaneous perfusion at 3 distinct regions of interest (ROI) within the hands was undertaken using LSCI and infrared thermography (IRT) at baseline, and at 13s intervals over 15 min following a standardised local cold challenge. Endpoints for evaluation included absolute measurements at baseline and following cold stress, in addition to the characteristics of the re-warming curves (maximum % recovery and maximum gradient). Visits 1 and 2 were undertaken in identical conditions (ambient temperature 23°C) to assess reproducibility, whereas visit 3 was undertaken at a lower ambient room temperature of 18°C to evaluate responsiveness to reduction in ambient room temperature. RESULTS: Fourteen healthy participants completed the study. There was greater variability in the data generated using LSCI compared with the highly damped IRT, reflecting greater sensitivity of LSCI to physiological variation and movement artefact. LSCI and IRT correlated well at baseline and following cold challenge for all endpoints (r(s) for pooled data between 0.5 and 0.65, p<0.00005). Reproducibility of both IRT and LSCI was excellent (ICCs>0.75) for absolute assessments but lower for re-warming curve characteristics. LSCI provides greater spatial resolution than IRT identifying variation in cutaneous perfusion within the hands most likely associated with the presence of arteriovenous anastamoses. Both techniques were responsive to reduction in ambient room temperature. Effect sizes were greatest for IRT than LSCI (e.g. -1.17 vs. -0.85 at ROI 1 at baseline) although this may represent heat transfer rather than altered vascular perfusion. DISCUSSION: In the dynamic assessment of digital vascular perfusion, LSCI correlates well with IRT, is reproducible and responsive to reduction in ambient room temperature. Absolute measurements appear preferable to parameters derived from re-warming curve characteristics when assessing digital perfusion following cold challenge. The greater temporal and spatial resolution of LSCI compared with IRT may facilitate the development of novel assessment tools of autonomic function and digital cutaneous perfusion.

Influence of the cold challenge on the discriminatory capacity of the digital distal-dorsal difference in the thermographic assessment of Raynaud's phenomenon.

OBJECTIVES: To investigate the influence of a standardised cold stress test (CST) on the thermographic 'distal-dorsal difference' (DDD) and its capacity to differentiate between disease states in the assessment of Raynaud's phenomenon (RP), and to compare the discriminatory capacity of the DDD of individual digits with composite indices of multiple digits. METHODS: Thermographic images of 55 patients with primary RP (PRP, n=27) and systemic sclerosis (SSc, n=28) who had undergone assessment of RP were retrospectively reviewed. The DDD for individual digits, and composite scores of multiple digits, were calculated at baseline (23°C), and at 10 min following CST. The discriminatory capacity of the mean DDD, and the proportion of patients with a clinically meaningful DDD of <-1°C, were assessed for individual digits and composite indices, at baseline and following cold challenge. RESULTS: There was a more pronounced decrease of the DDD (indicating reduced distal perfusion) following CST in patients with PRP compared to SSc. The disparity in response to CST between groups narrowed the differences that were present at baseline, reducing the discriminatory capacity of the DDD for all endpoints. Sparing of the thumbs occurs to a greater extent in SSc (P<0.005) compared with PRP (P<0.05) but does not facilitate differentiation between groups. Large variability of the DDD within groups precludes easy differentiation between disease states. Composite indices of multiple digits are preferable to individual digital assessment. CONCLUSIONS: The discriminatory capacity of the DDD is lost following CST. The CST may not be essential in the thermographic assessment of RP, potentially allowing greater use of thermography in clinical practise.