Performance of three enzyme immunoassays and two direct fluorescence assays for detection of Giardia lamblia in stool specimens preserved in ECOFIX

ECOFIX is a single-vial stool preservative that is both formalin- and mercu ry-free, We evaluated the abilities of three commercial Giardia lamblia-spe cific enzyme immunoassays (EIAs) (ProSpecT Giardia Microplate Assay [Alexon -Trend Inc,], Giardia Test [Techlab], and Premier Giardia lamblia [Meridian Diagnostics, Inc,]) and two commercial direct fluorescent-antibody (FA) as says for G. lamblia (Crypto/Giardia IF Test [Techlab] and Merifluor Cryptos poridium/Giardia [Meridian Diagnostics, Inc.]) to detect G. lamblia in 34 G , lamblia positive and 44 G. lamblia-negative stool specimens (determined b y traditional examination for ova and parasites) preserved in ECOFIX compar ed to their abilities to detect G. lamblia in the same specimens preserved in formalin as the "gold standard" for each assay. Of the 34 formalin fixed positive specimens, the number detected by each assay was as follows:, Ale xon EIA, 34; Meridian EIA, 27; Techlab EIA, 29; Meridian PA assay, 31; and Techlab FA. assay, 28, Both FA tests and the Alexon ELA performed well with ECOFIX, but the other two EIAs detected fewer positive specimens (the diff erence was statistically significant with the Techlab EIA) when ECOFIX was the preservative. Use of G. lamblia cyst antigen from cultured organisms pr eserved in formalin and ECOFIX demonstrated that the Alexon EIA could detec t smaller amounts of antigen in ECOFIX than the other two EIAs could and su ggested that cyst antigen is more stable in formalin, We recommend that lab oratories use an FA assay or the Alexon EIA if they plan to use ECOFIX as t heir stool preservative.