Report Non-invasive method distinguishes chronic telogen effluvium from mild female pattern hair loss: clinicopathological correlation Caroline Bittencourt 1 , MD, Fernanda Teixeira 2 , PhD, Daniela A. Ferraro 1 , MD, Tania C.B. Soares 1 , PhD, Aparecida M. Moraes 3 , PhD, and Maria L. Cintra 1 , PhD 1 Department of Pathology, Medical School, State University of Campinas, Campinas, Brazil, 2 Department of Dermatology, Ealing Hospital, London, UK, and 3 Department of Dermatology, Medical School, State University of Campinas, Campinas, Brazil Correspondence Maria Leticia Cintra, PhD Department of Pathology Medical Sciences School State University of Campinas (UNICAMP) Rua Tess alia Vieira de Camargo, 126 Cidade Universit aria Zeferino Vaz Campinas S~ ao Paulo 13083-887 Brazil E-mail: marialet@fcm.unicamp.br Conflicts of interest: None. Abstract Background The distinction between chronic telogen effluvium (CTE) and female pattern hair loss (FPHL) is important because of their different prognosis and treatment. Non- invasive methods have been described to be useful in differentiating FPHL from CTE. This prospective study investigated the use of the washing method to differentiate CTE from mild FPHL. Methods Twenty patients with CTE and 17 with FPHL were recruited and followed for 18 months. The diagnosis was established through clinical, laboratory, and histological studies. The patients were asked to abstain from washing their hair for 5 days and then shampoo and collect all hair shed in the process. Hair shafts were then counted and divided into two groups: up to 3 cm in length or longer. Results In the CTE group, the mean hair count was high (438), and in all cases, <10% were short. In patients with FPHL, the mean count was not as high (215) and in only one patient, short hairs comprised <10% of the total. The greater the number of long hairs, the higher was the density of terminal follicles seen histologically. The CTE group presented a greater number of patients with serum iron values <70 lg/dl. Ferritin levels ranged from 6.98 to 128.33, average of 66.65 (CTE), and 16.5–304.8, average of 114.97 ng/ml (FPHL), but no significant differences were found. Conclusion The washing test can be useful to avoid biopsy procedures. Iron serum levels are possibly an additional parameter that may improve CTE diagnosis if combined with an earlier test. Introduction Chronic telogen effluvium (CTE) is a poorly understood condition affecting predominantly women and character- ized by diffuse shedding of hair for more than 6 months. 1 There is considerable loss, but the patients appear to have a full head of hair, as it takes at least a reduction of 25% for thinning to be evident. 2 Even when daily shedding is twice normal (about 200 hair shafts), new hair is continu- ously produced, canceling the deficit. 2 Clinical and laboratory examinations have failed to find any organic cause, nutritional disorder, medications, or triggers preceding hair loss. 3 The pathogenesis of CTE is unknown, and a diagnosis is made after exclusion of other causes of diffuse telogen shedding, such as anemia, nutritional deficiency, changes in thyroid, kidney, and liver function, and use of drugs associated with hair loss. 4 The most important CTE differential diagnosis is incip- ient female pattern hair loss (FPHL); 4 both share the same age range of onset and, as in initial FPHL, hair shedding in CTE can be diffuse and episodic. 5,6 Their dif- ferentiation may be difficult, 1 and it has been suggested that CTE precedes FPHL. 4 However, a long follow-up study showed that four of five patients with chronic hair loss did not progress to FPHL. 7 In case of doubt, a biopsy can be performed to confirm the diagnosis of CTE so that the patient can be reassured that lost hairs will be replaced by new ones. 1 A non-invasive method can be used to differentiate CTE from FPHL: 8 the patient collects all hair shed at the time of hair washing after a period of 5 days without shampooing. In addition to counting the hairs, a length measurement is performed to estimate the percentage of short hairs (≤3 cm). When these represent >10% of all collected shafts, 9 the diagnosis of FPHL is considered. If ª 2015 The International Society of Dermatology International Journal of Dermatology 2016, 55, e373–e379 e373