Cellulitis in Children: Risk Factors for Developing Cellulitis and Risk Factors for Hospitalisation with Cellulitis

Abstract

Background: Cellulitis is a significant health issue for New Zealand children. It is a common and increasing problem and is associated with significant ethnic and socioeconomic disparities. Hospital admissions for cellulitis are as common as admissions for pneumonia, but far less is known about the management and even less about the risk factors. Cellulitis is the end result of a series of events: from an initial breach of skin, to infection, to cellulitis requiring medical treatment, through to cellulitis requiring hospitalisation. This process takes several days to evolve with several factors influencing whether a child subsequently develops a skin infection or requires hospitalisation following the initial event. These include host susceptibility and behaviours, social and environmental factors, microbiological factors, health literacy, and healthcare factors. At present the relative importance and contribution of each of these factors is ill-defined. Many of these factors have been specifically examined among adults, but no studies have specifically examined risk factors for cellulitis among children. Aims: The specific aims of this thesis were to identify and quantify the risk factors associated with developing cellulitis, and to identify and quantify the risk factors associated with hospitalisation in children who have developed cellulitis. Methods: Our research started with an exploratory case series of 100 children admitted to Starship Children’s Hospital with cellulitis. The case series provided the opportunity to explore pathways to care for children, pilot questions, and generate hypotheses for future research. We then undertook an HRC funded case-control study using complex survey methodology to address the specific aims of the project. The prospective case-control study occurred over a 12 month period: June 2001-May 2002. Eligible children were 0-14 years of age, in the Auckland and Waitemata District Health Board catchment areas, with a nominated General Practitioner. There were 3 groups: 1. Children with cellulitis who required hospitalisation (Hospital cases), 2. Children with cellulitis successfully treated in primary care (GP cases), and 3. Children without cellulitis in the community (Controls). Results: Seven hundred and seventy eight children were enrolled: 227 Hospital cases, 145 GP cases and 395 controls. Māori children were at 4 times the risk (aOR 4.04, 2.32-7.02) and Pacific children 6 times the risk (aOR 6.11, 3.42-10.89) of developing cellulitis than other New Zealand children. Infants and preschool children were less likely to develop cellulitis than school-age children (aOR 0.13, 0.05-0.33, and aOR 0.53, 0.34-0.82 respectively). Risk factors for developing cellulitis included socioeconomic factors (a maternal community services card, smokers in the home, sharing a bedroom), and insect bites in the previous week. A past or family history of cellulitis significantly increased the risk of developing cellulitis. Having an identified health problem reduced the risk of developing cellulitis. Host behaviours such as scratching insect bites or eczema until they bled were associated with an increased risk of cellulitis. Children in families who reported difficulties accessing healthcare were at increased risk of developing cellulitis. Once cellulitis developed, ethnicity was not associated with hospitalisation, however, infants were at increased risk (aOR 6.7, 1.45-30.94). Children with a preceding insect bite were less likely to require admission as were children with a past or family history of cellulitis. Several hygiene behaviours were associated with an increased risk. Increased health literacy reduced the risk of hospitalisation (administration of first aid for redness, antibiotic cream, visiting own GP). Size >50 mm at first visit to a health care professional, difficulties accessing healthcare and no additional healthcare advice given by the healthcare professional all increased the risk of hospitalisation. Conclusions: Cellulitis is a complex disease with overlapping effects of several risk factors. No one factor dominates. Our research has highlighted the persisting effect of ethnicity irrespective of other associated factors. Pacific children are more than 6 times the risk, and Māori children more than 4 times the risk of developing cellulitis compared to other New Zealand children. This is a significant cause of inequity and deserves further exploration into underlying genetic susceptibilities in immune responsiveness. Cellulitis in children is a recurring household disease due to a combination of factors rather than a recurrent disease of individuals due to local factors. Behavioural and environmental factors are more important than individual factors. Insect bites are an important factor in both the development of cellulitis and the risk of hospitalisation with cellulitis. This has been underappreciated and needs specific intervention. Health literacy is key with important factors identified in caregivers’ awareness of the integrity of their child’s skin as well as differing management of both breaches of skin and the first signs of infection. Key messages must include regular checking of the skin, as well as advice about skin health and first aid management at the first sign of redness. Healthcare factors play an important role in both the development of and hospitalisation with cellulitis. Access to primary care is key as well as the provision of general advice regarding skin care and health. This research work has increased our understanding and identified several important risk factors for cellulitis and hospitalisation with cellulitis among children. This will assist in the development of management and prevention strategies to reduce the incidence and impact of cellulitis among children and their families.