Background Raynaud's phenomenon (RP) is a disorder characterized by paroxystic episodes of vasospasm of digital arteries following cold exposure or emotional distress. Infrared thermography detects temperature distribution of the skin and gives an indirect measure of microvascular flow. To date there is no evidence of the application of this method in pediatric age for evaluation of RP and differentiation from other conditions, such as acrocyanosis.
Objectives 1. To determine the reliability and reproducibility of thermography by comparing inter-observer concordance in thermal imaging interpretation; 2. To evaluate the diagnostic value of thermographic detection of extremities re-warming following cold challenge test by comparison between healthy controls and children with microvascular alterations (primary RP, secondary RP and acrocyanosis).
Methods 41 children were included in the study: 20 with RP (including primary and secondary RP), 8 with acrocyanosis and 13 healthy controls. All assessed subjects underwent the same cold challenge protocol under standardised conditions: baseline images of both hands were taken following acclimatisation at 23 °C for 15 min and then, patients submerged their gloved hands in a water bath at 15 °C (±1 °C) for 1 minute. Repeated thermal images were obtained in the 10 minutes following cold challenge (at 1 minute interval each). The temperature in the dorsal aspect of metacarpophalangeal joint and of the distal interphalangeal joint of each finger excluding the thumb was measured for 12 times respectively (T basal, T0-10). Two clinicians reviewed the thermal images and measured the temperature values independently. Interclass correlation coefficient (ICC) was calculated in each sites (metacarpophalangeal and interphalangeal joints) of each hand for all times in order to determine the inter-observer agreement. The modality of the rewarming in each group was evaluated considering the mean value between the two different operators' measurements and calculating the average temperature among different time intervals (ΔT). The average temperature variation (Δ°C) was analysed as a function of the site (right and left hand; metacarpophalangeal and interphalangeal joint). We accomplished our analysis considering two different time intervals: Tn-Tn-1 and Tn-T pre (where n designates the minutes of observation and pre the baseline). The differences in re-warming curves between RP and acrocyanosis were performed by calculating the mean longitudinal thermal gradient (Δ MCF-IFD) in each finger and time of observation.
Results The ICC showed a full inter-observer agreement between the two clinicians (range 0.93-0.96). The temperature variation in the 10 minutes following cold challenge compared with the baseline temperature showed statistically significant differences between children with microvascular alterations (RP and acrocyanosis) and healthy controls (p<0.001).
The analysis of the longitudinal thermal gradient (Δ MCF-IFD) showed statistically significant differences in the comparison of patients with RP and acrocyanosis regarding re-warming modality of single fingers (p<0.05).
Conclusions This study demonstrates, for the first time in the pediatric age, that thermography after cold challenge has an excellent inter-observer reproducibility and it is reliable in identification of pathological microvascular behaviour.
Disclosure of Interest None declared
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