Positive control reference specimens

Positive control specimens should always be used when available. Methods of preparation of some of these are described under techniques for specific parasites. For use with

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the formol-ethyl acetate method for concentration of stool specimens, Bayer's fixative is preferable to formalin for preserving cyst morphology in specimens used for quality control (Moody 1986). Bayer's fixative (stock solution): copper chloride dihydrate (CuCl2 ■ 2H2O), 7g: glacial acetic acid, 70

ml: 20% v/v formalin solution, 1 000 ml (200 ml 37-40% formaldehyde mixed with 800ml distilled water). Store at RT; stable indefinitely.

For use: dilute the stock solution 1 in 10 with distilled water.

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