When searching for a lab partner, ensure they are accredited to the ISO/IEC 17025 Testing and Calibration Laboratories standard. This way you know they conduct testing using industry accepted procedures for labs. The link below contains info on the ISO standard. This is an international standard.
https://www.iso.org/ISO-IEC-17025-te...oratories.html
https://www.iso.org/ISO-IEC-17025-te...oratories.html