▁from ▁the ▁tip - edge ▁to ▁the ▁cut icle ; ▁sharp ▁pe aked ▁" ro of - ridge " ▁raised ▁lines ▁from ▁cut icle ▁to ▁tip ; ▁or ▁separation ▁of ▁super f icial ▁layers ▁of ▁the ▁n ail ▁followed ▁by ▁loss ▁of ▁patch es ▁of ▁these ▁super f icial ▁layers , ▁leaving ▁thin ▁red ▁n ails ▁beneath ; ▁or ▁n ail ▁p itting – p unct ate ▁changes ▁along ▁the ▁n ail ▁plate ▁surface . ▁ ▁C aus es ▁The ▁causes ▁of ▁n ail ▁ps or ias is ▁are ▁unknown . ▁ ▁It ▁has ▁been ▁suggested ▁that ▁fung i ▁may ▁play ▁a ▁role . ▁ ▁Di agn osis ▁The ▁N ail ▁Ps or ias is ▁Sever ity ▁Index ▁( N AP SI ) ▁is ▁a ▁numeric , ▁reprodu cible , ▁objective , ▁simple ▁tool ▁for ▁evaluation ▁of ▁n ail ▁ps or ias is . ▁ ▁It ▁evalu ates ▁several ▁signs ▁separately , ▁each ▁on ▁a ▁ 1 – 3 ▁scale : ▁p itting , ▁Beau ' s ▁lines , ▁sub ung ual ▁hyper ker atos is ▁and ▁on ych ol ysis . ▁ ▁A ▁ 2 0 0 5 ▁study ▁proposed ▁a ▁modified ▁N AP SI ▁scale ▁for ▁persons ▁with ▁ps or ias is ▁and ▁named ▁the ▁title ▁of ▁their ▁publication ▁" Mod ification ▁of ▁the ▁N ail ▁Ps or ias is ▁Sever ity ▁Index ". ▁ ▁Then , ▁in ▁ 2 0 0 7 , ▁a ▁study ▁found ▁that ▁there ▁was ▁a ▁high ▁level ▁of ▁inter - r ater ▁vari ability ▁of