Around 4,000 tests are estimated to be affected in Wales, more information is available in the statement from the Minister for Health and Social Services.
Amcangyfrifir bod tua 4,000 o brofion sydd wedi cael ei effeithio yng Nghymru, mae fwy o wybodaeth ar gael yn y datganiad gan y Gweinidog Iechyd a Gwasanaethau Cymdeithasol.