CORRESPONDENCE Clinical and Experimental Allergy The investigation of chronic urticaria in childhood: which investigations are being performed and which are recommended? P. Thomas à , M. R. Perkin w , N. Rayner à , H. Cox z , A. T. Fox w , S. Leech ‰ , G. Lack z and G. du Toit z à Imperial College School of Medicine, London, UK, w St George’s, University of London, London, UK, z St Mary’s Hospital, London, UK, ‰ Paediatric Allergy Department, King’s College Hospital, London, UK and z Children’s Allergy Service, Evelina Children’s Hospital, Guy’s & St Thomas’ NHS Foundation Trust, Kings College London, London, UK Chronic urticaria (CU) is diagnosed on the basis of experiencing frequent weals, with or without angioedema, for 46 weeks. The most commonly identified avoidable precipitants are physical triggers such as exposure to pressure or cold. The prevalence of CU in the UK remains uncertain [1–3]. CU has been shown to significantly impair the quality of life of suffers [4]. The precise pathophysiology of CU remains unknown; however, func- tional circulating antibodies (of the IgG1 and IgG3 sub- class) directed against the FCeRIa or IgE have been demonstrated in a significant portion of both adults and children with CU [5, 6]. The British Society for Allergy and Clinical Immunol- ogy (BSACI) has recently joined the European Academy of Allergy and Clinical Immunology (EAACI/GA 2 LEN/EDF) in publishing recommendations for the investigation of CU [7, 8]. The BSACI makes specific recommendations for the investigation of CU in children. The BSACI recom- mendations state ‘if the clinical history and examination are typical of chronic idiopathic urticaria, then further laboratory investigations are rarely useful’. The recom- mended investigations are in two tiers; firstly, ‘if the clinical history suggests a candidate allergen, then allergy tests (skin testing or specific IgE tests) are warranted.’ A second tier of ‘additional investigations’ are also sugges- ted–if clinically indicated; these include, urine analysis, full blood count (FBC), erythrocyte sedimentation rate (ESR), liver function tests (and viral hepatitis screen if elevated) (LFTs), coeliac disease screen, thyroid function and anti-thyroid antibodies (TFTs), cold, dermographism and pressure provocation tests, elimination re-challenge diets, antinuclear antibodies (ANA), skin biopsy, comple- ment/C1 inhibitor assays (C3/C4/C1 esterase), serum cryo- proteins and an infectious disease screen (past/current viral, bacterial or parasitic). We performed a retrospective chart review of children attending three London-based Paediatric Allergy Clinics with CU over a 24 month period. Hospital database searches were performed; search terms included: CU, pressure urticaria, cold urticaria and chronic idiopathic urticaria. Patient summary letters were then scrutinized to ensure that the study criteria for a diagnosis of CU had been met and the selection of investigations (and results thereof) were recorded. Statistical analysis was performed using Stata 8.2 [9]. Data collection was entirely anonymous. One hundred and seventy two patients (age o18 years) met the criteria for CU at initial assessment. The median age was 11 years and 1 month (range 2 years 3 months–18 years) and there was equivalent male–female ratio. Frequency of investigations Figure 1 demonstrates the frequency with which the children underwent testing. No investigations were per- formed for 17% (30/172) of children with CU, 36% (62/ 172) underwent a single investigation and 47% (80/172) 4 1 investigation. Of the children who underwent a single investigation, 24% of these investigations were for one of the ‘additional investigations’ and 76% an allergy inves- tigation (skin prick test and/or specific IgE test). The mean number of investigations performed per child was 2.07 [95% confidence interval (CI) 1.80–2.35]. No patient underwent the entire panel of investigations with the maximum number of tests undertaken for a single child being seven. With regard to the specific investigations, the results were essentially dichotomized, with six tests oc- curring relatively frequently (FBC, ESR, LFTs, TFTs, ANA and C3/C4/C1 esterase) and the rest being performed rarely, if at all. Investigation outcomes Of the 60% (104/172) of children who underwent an allergy test, 41% of them (43/104) were positive (i.e. Clinical and Experimental Allergy, 38, 1061–1062 doi: 10.1111/j.1365-2222.2008.02975.x  c 2008 The Authors Journal compilation  c 2008 Blackwell Publishing Ltd