Effect of Freezing-thawing and Storage Time on Some Specific Human Enzymes

The present research was designed and conducted to study the effect of freezing-thawing and storage time on some specific human enzymes. The enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) were analysed immediately after sample collection, after undergoing freeze thaw at – 4°C, – 20°C and –70°C at day o and after 7 days of storage at – 4°C, – 20°C and –70°C. A total of 50 healthy males and 50 healthy females were used for the study and sample collection was by pooled serum. Our results show that there was no statistically significant difference (p>0.05) between AST, ALT, ALP and CPK levels obtained after freeze-thaw at – 4°C, – 20°C and –70°C at day 0 when compared with the control for both males and females. Also, no statistically significant difference (p>0.05) was seen in the levels of AST, ALT, ALP, CPK analysed after 7 day storage at – 4°C, – 20°C and –70°C in both males and females when compared with the control. However, there was a significant difference (p<0.05) in the levels of LDH obtained after freeze-thaw at – 4°C both at day 0 and after 7 days of storage. In conclusion, the results showed that the specific enzymes studied were most stable when stored at –70°C for 7 days assuming sample analysis is not carried out shortly after sample collection.