Abstract
BackgroundSkin neurofibromas represent one of the main clinical manifestations of neurofibromatosis 1, and their number varies greatly between individuals. Quantifying their number is an important step in the methodology of many clinical studies, but counting neurofibromas one by one in individuals with thousands of tumors is arduous, time-consuming, and subject to intra and interexaminer variability. We aimed to evaluate the efficacy of a new methodology for skin neurofibromas quantification using paper frames.MethodsThe sample comprised 92 individuals with NF1. Paper frames, with a central square measuring 100 cm2, were placed on the back, abdomen and thigh. Images were taken, transferred to a computer and two independent examiners counted the neurofibromas. The average number of neurofibromas/100 cm2 of skin was obtained from the mean of the three values. The differences in the quantity of neurofibromas counted by two examiners were evaluated with Intraclass correlation coefficient (ICC), paired t-test, Bland-Altman and survival-agreement plots. To evaluate the predictive value of the method in obtaining the total number of neurofibromas, 49 participants also had their tumors counted one by one. Reproducibility was assessed with Pearson’s correlation coefficients and simple linear regression model.ResultsThere was excellent agreement between examiners (ICC range 0.992-0.997) and the total number of skin neurofibromas could be predicted by the adhesive frames technique using a specific formula (P < 0.0001).ConclusionsIn this article we describe a reliable, easy and rapid technique using paper frames to quantify skin neurofibromas that accurately predicts the total number of these tumors in patients with NF1. This method may be a useful tool in clinical practice and clinical research to help achieve an accurate quantitative phenotype of NF1.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-014-0202-9) contains supplementary material, which is available to authorized users.
Highlights
Skin neurofibromas represent one of the main clinical manifestations of neurofibromatosis 1, and their number varies greatly between individuals
Our aim was to evaluate the efficacy of a new methodology for skin neurofibromas quantification using paper frames, investigating interexaminer reliability and value of the approach in predicting the total number of skin tumors
The mean age was 35.6 (± 15.2) years. Regarding these 49 Neurofibromatosis 1 (NF1) individuals who had the total number of neurofibromas evaluated, the number of tumors strongly varied with age (r = 0.633, P < 0.0001); older individuals had higher number of neurofibromas
Summary
Skin neurofibromas represent one of the main clinical manifestations of neurofibromatosis 1, and their number varies greatly between individuals. Quantifying their number is an important step in the methodology of many clinical studies, but counting neurofibromas one by one in individuals with thousands of tumors is arduous, time-consuming, and subject to intra and interexaminer variability. Neurofibromatosis 1 (NF1, OMIM 162200) is a common autosomal dominant genetic disorder caused by mutations in the NF1 gene It presents extremely variable expressivity and can cause diverse clinical manifestations, including café-au-lait spots, axillary and inguinal freckling, Lisch nodules, and multiple benign peripheral nerve sheath tumors called neurofibromas [1,2]. NF1 individuals are categorized according the number of neurofibromas, and some authors do not report if the categorization was performed based on counting neurofibromas one by one or if the exact number of tumors was not obtained and an estimative of their number was used, which is subject to variability [3,12,13,14,15,16]
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