Summary of significant accounting policies (Details) - Amount of expense related to share-based payment arrangements - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share Based Compensation	$ 525	$ 429	$ 594
Cost of Clinical Laboratory Services [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share Based Compensation	6	5	9
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share Based Compensation		2	1
Selling, General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share Based Compensation	$ 519	$ 422	$ 584