Some countries approve antigen tests, others require that the analysis of the PCR test be performed by a laboratory accredited according to ISO 17025 or ISO 15189. At www.coronapassport.se you will find updated information, country by country, which is available from the Swedish Ministry of Foreign Affairs and IATA.
Fysiotest offers PCR and antigen tests for ongoing infection, antibody tests after infection and issues certificates according to the requirements of each country.