Systematic monitoring of standardization and harmonization status with commutable EQA-samples-Five year experience from the Netherlands

► Equivalence of lab results worldwide is a major mission for medical laboratories. ► Commutable sera have been introduced to evaluate the degree of test equivalence. ► Median interlab CVs became < 5% for electrolytes/substrates, and < 10% for enzymes. ► Amelioration is mainly explained by improved method standardization. ► Commutable samples in EQAS are a powerful instrument to evaluate test equivalence.