Protocol for extraction and enzyme immunosorbent assay (ELISA) of progesterone or estradiol from human salivary samples preserved with or without sodium azide (protocol v1.0).

Abstract

Field research in remote areas presents many challenges, often including a lack of facilities and resources for maintaining a cold chain to preserve samples at low temperatures until they can be assayed in a laboratory. Cold-chains are necessary for the storage and transport of many types of biological samples (e.g., blood, urine and saliva) in order to reduce degradation and inhibit bacterial and fungal growth. One alternative to a cold chain is to add sodium azide, a potent antimicrobial, to each biological sample. However, sodium azide is incompatible with commercial enzyme immunoassay (EIA) kits that use horseradish peroxidase, an enzyme inactivated by sodium azide. To address this problem, we tested and validated EIA protocols that use an alternative enzyme, alkaline phosphatase. These protocols can be used for the measurement of steroid hormones in salivary samples that have been preserved with sodium azide, thus eliminating the trouble and expense of maintaining a cold chain from the field to the lab.