Sometimes, request for additional medical tests come after the applicant has submitted eAPR. In your case, if you have time to submit your eAPR, would suggest to wait to complete the additional tests and then submit eAPR.
Meanwhile, contact the clinic and find out whether they would issue any new documents or Acknowledgement Form after the additional tests. If not, and if you do not have time to wait to submit eAPR, you can submit it. Just ensure that you submit copy of the above email and proof of having taken an appointment with the PP and explain the same in LOE. Post the test, intimate CIC via IRCC Webform, but ensure that everything is done at the earliest.