Abstract: Objective To explore the value of serum Vitamins B12（VitB12）, folate and lactate dehydrogenase(LDH) detection in differential diagnosis of myelodysplastic syndrome(MDS) and megaloblastic anemia(MA). 
Methods The clinical data of 41 MDS and 66 MA patients were retrospectively analyzed. Another 50 healthy people were selected as the control group. The clinical symptoms of the three groups were observed and their serum VitB12, folic acid and LDH were compared. Its diagnostic efficiency was determined by the ROC curve. 
Results The infection rate and bleeding rate in the MA group were lower than those in the MDS group, but the rate of anemia was higher than that in the MDS group(P＜0.05). The VitB12 levels in the MA group were higher than those in the MDS and control group, while the LDH value was significantly higher than that in the MDS group and the control group(P＜0.05). No significant difference was found in folic acid among three groups(P>0.05). The area under the curve(AUC) of VitB12, folic acid, and LDH for diagnosis of MDS was 0.741, 0.531, and 0.948, respectively. When VitB12 was higher than 139.355, the sensitivity was 100.0% and the specificity was 84.0%; When folic acid was higher than 8.960, the sensitivity was 43.9% and the specificity was 94.0%; when the LDH value was higher than 200.670, the sensitivity was 98.5% and the specificity was 100.0%. The LDH value was the most valuable in diagnosing MDS patients. The AUC of VitB12, folic acid, and LDH for the diagnosis of MA was 0.868, 0.545, and 0.991, respectively. When VitB12 was higher than 139.355, the sensitivity was 100.0% and the specificity was 84.0%; when folic acid was higher than 8.960, the sensitivity was 43.9% and the specificity was 94.0%; when the LDH value was higher than 200.670, the sensitivity was 98.5%, and the specificity was 100.0%. Therefore, both VitB12 and LDH had a high diagnostic value for MA. 
Conclusion Serum VitB12 and LDH detection have a certain effect on the differential diagnosis of MDS and MA, but the diagnostic efficiency of LDH is relatively high. This is worthy of clinical application in the future and should be used reasonably according to the real situation of patients.

Key words: myelodysplastic syndromes, anemia, megaloblastic, diagnosis, differential