Outcome measures
All participants had their scar assessed after three weeks, six months and twelve months after removal of the CVC. The assessment was conducted by a study nurse and a dermatologist. The dermatologist had fewer observations than the study nurse. The study nurse assessed the scar by using the Vancouver Scar Scale (VSS) [8] and the Patient and Observer Scar Assessment Scale (POSAS) version 1 [9] at each clinical check every three weeks, six months and twelve months, after removal of the CVC. The parents and patients assessed the POSAS three weeks, six months and twelve months at the clinical check. Digital clinical images of the scar were taken after three weeks, six months and twelve months after removal of the CVC by a professional clinical photographer affiliated with Aarhus University Hospital. In all pictures, a ruler was applied to the skin, allowing the scar width to be standardized. The clinical images were provided blinded to the dermatologist for assessment of VSS and scar width. In the present study, the dermatologist categorized the interventions groups´ skin type according to Fitzpatrick skin type classification scale [10]. Patients with a Fitzpatrick 3 or higher skin type are more likely to develop keloid scar formation [11]. However, this is not clear for hypertrophy [12].
The VSS assesses four variables: Pigmentation, pliability, height and vascularity. It has a total score of 14, where 0 is equivalent to the patients´ normal skin [9]. The POSAS consists of two scales: One completed by the patient and one by the observer. The patients’ scale contains six questions with regards to relief, pain, color, pliability, thickness and itching. The observer scale involves five questions regarding to pliability, thickness, relief, pigmentation and vascularity. Each parameter uses a 10-point scoring system, with 1 representing normal skin and 10 corresponding to the worst imaginable scar. The total score of the patient scale consists of adding the scores of each of the six items from 6 to 60. The observer scale consists of five items and therefore, the total score ranges from 5 to 50. At total score of 6 and 5, respectively, reflects normal skin [9]. The main outcome was the Vancouver Scar score. Secondary outcomes were scar width and scar quality measured using the POSAS.