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Table 4 Item-total correlations and Cronbach’s alpha with item deletion for the EPP Symptoms score (Cronbach’s alpha for scale =0.954) from Visit 3 only

From: Validation of a novel patient reported tool to assess the impact of treatment in erythropoietic protoporphyria: the EPP-QoL

 

Corrected Item-Total Correlation

Cronbach’s Alpha if Item Deleted

Item 4: Over the last 2 months, how much has EPP influenced the choice of the clothes you wear on a sunny day?

0.762

0.951

Item 5: Over the last 2 months, how often did you feel you were at risk of developing EPP symptoms?

0.707

0.953

Item 6: Over the last 2 months, how much has EPP affected any social or leisure activities on a sunny day?

0.854

0.947

Item 7: Over the last 2 months, how much has EPP influenced your need to plan before leaving your house?

0.803

0.949

Item 8: Over the last 2 months, has EPP limited your ability to undertake activities in a spontaneous manner?

0.875

0.946

Item 10: Over the last 2 months, how much has EPP interfered with your going shopping or looking after your home (indoors and outdoors) or garden on a sunny day?

0.813

0.949

Item 11: Over the last 2 months, how much has EPP preventing you from attending outdoor social activities with family and friends?

0.871

0.947

Item 12: Over the last 2 months, how much has EPP limited your amount of outdoor activities?

0.885

0.946

Item 13: Over the last 2 months, how often did you experience typical EPP skin complaints?

0.720

0.952

Item 15: Over the last 2 months, how much has EPP influenced your method of transportation or seating preference during transportation?

0.754

0.951