In the case of accreditation of multiple site laboratories, can the head of the central laboratory transfer the power to approve and issue the test report to the head of the site laboratory?
There is no such requirement in the Standard that in the case of multisites test reports are approved and issued only by the head of the central laboratory (nor who can perform this activity in any case).
The laboratory (management) shall ensure which personnel have the competence to report/review results and authorise the test report as per cl. 6.2.6 and 7.8.2.1o. In multisites it makes more sense that this authorisation is given to personnel that are on site and involved in the day to day activities.
As multi sites, nowadays, normally are linked with LIMS with the central laboratory and personnel from there could be authorised to have access to the data and information (as per cl. 7.11) then test reports could be approved and issued by an authorised personnel from the central lab, if needed.
However, we shall take in mind that there might be areas that are regulated and there are legislative requirements that define who is responsible for authorising test reports.