(b) While stirring, heat gently to about 75 degrees centigrade until the
powder dissolves and the solution clears.
(c) Upon cooling, the solution should be clear. Solutions prepared from
some lots of PVA may be slightly turbid and contain some precipitate. Unless these are
excessive, the solution is satisfactory.
(a) Polyvinyl alcohol (PVA) fixation-preservation in vials.
STEP 1: Stool specimens should be immediately submitted to the laboratory or fixed at
the site of collection.
STEP 2: With applicator sticks, thoroughly mix in a labeled bottle one part (five grams)
feces with three parts (15 grams) of PVA fixative. The fixative should be
employed at room temperature or up to 50 C. This step should be performed
immediately on receipt of the specimen.
STEP 3: Dip the screwcap and top portion of the bottle two or three times into a hot,
melted paraffin bath to prevent leakage and evaporation upon storage.
(b) PVA fixation-preservation on microscope slides.
STEP 1: Stool specimens should be immediately submitted to the laboratory.
STEP 2: With an applicator stick, immediately mix one part of the specimen with three
parts of PVA-fixative on a microscope slide. Three drops of mixed, bottled,
PVA-fixed feces may also be spread onto a microscope slide. (The best yield
of trophozoites or cysts is from the finely dispersed upper layer of the
STEP 3: Spread (do not smear) the mixture over one-third of the slide. To prevent later
peeling, extend the specimen to the edges of the slide.
STEP 4: Allow the mixture to dry thoroughly (preferably overnight at 35 C). Dry films
remain satisfactory for staining for several months.
(a) Commercially available vials and bottles are available.
(b) If the specimen has been stored for long periods in PVA and become
jelled, it can be liquified by heating in a water bath. (Set at 37 to 50 C.)