D dimer result 78 cut off 250 is this good ?

YES: You are in the normal range for your lab

See answer : D-dimer assay, combined with clinical information, including pretest disease probability) is primarily used to help determine the possibility of either deep venous thrombosis/DVT (blood clot in the leg) or acute pulmonary embolism/PE (blood clot traveled to the lungs). Normal D-dimer values <250 ng/mL excludes DVT/PE with 95% accuracy when there is low or moderate pretest probability of DVT/PE.