Effect of hemolysis on D-dimer testing measured with the Improgen kit: is all manufacturer information correct?

D-dimer is a fibrin degradation product and its measurement is affected by hemolysis. This study was designed to reveal the value of hemolysis affecting D-dimer in our laboratory. In this study, hemolysate samples obtained by both mechanical and freezing methods were used. D-dimer levels of all plasmas were measured with Improgen Diagnostic kit by immune-turbidimetric method. Numerical change in hemolyzed samples was evaluated by calculating the percentage difference, and clinically significant differences were evaluated by calculating the maximum acceptable bias (MAB). In the hemolysate study prepared by both freeze-thaw and mechanical methods, it was observed that low D-dimer levels did not exceed the total allowable error (TAE) (30%) up to +2 hemolysis (corresponds to hemoglobin = 1.01-2 g/l) and did not exceed the MAB (65%) even at +4 hemolysis (corresponds to hemoglobin = 1.01-2 g/l). High D-dimer levels did not exceed the limit values of both TAE (30%) and MAB (68%) even in +4 hemolysis. The D-dimer test was affected by lower levels of hemolysis compared to both other studies and the values in the kit insert (hemoglobin >5 g/l corresponds to +4 hemolysis index). We verified the hemolysis interference in the D-dimer test, which we thought was not compatible with the kit insert, under our own laboratory conditions. This is the first hemolysis interference study performed with the Improgen brand d-dimer kit. In samples with a hemolysis rate of +2 and above, it would be more accurate to reject the D-dimer result as a 'hemolyzed sample'.