Table 1.

The effect of storage temperature and duration on dried blood spot estimation of GPD enzyme activity

Storage temperature	Baseline G6PD enzyme activity (%) that results in a sample testing severely deficient (< 10% activity) at the designated storage temperature and duration				Decay in enzyme activity
	Day 1	Day 5	Day 10	Day 14
4°C	10%	10%	15%	15%	~ 5% by Day 10
25°C	10%	15%	25%	25%	~ 5% by Day 5
					~ 15% by Day 10
37°C	10%	15%	25%	50%	~ 5% by Day 5
					~ 15% by Day 10
					~ 40% by Day 14

The reliability of G6PD assays on blood spots stored for different times at different temperatures was assessed with bloodspots containing differing amount of reference G6PD enzyme activity. The table shows the % enzyme activity that tested as deficient (≤ 10% activity) at days 1, 5, 10 and 14 when stored at 4°C, 25°C and 37°C. The decay in enzyme activity represents the difference between the original enzyme activity and the activity when retested.