Fixatives for Preservation Advantages and Disadvantages

formalin

advantages:

• easy to prepare

• preserves specimens for up to several years

• long shelf life

formalin

disadvantages:

• doest not preserve parasites morphology for permanent smears

• trophozoites usually cannot be recovered

• morphologic details of cysts and eggs may fade with time

polyvinyl alcohol

advantages:

• preparation of a permanent stained smear

• long shelf life when stored at room temperature

polyvinyl alcohol

disadvantages:

• recovery of certain parasites that is not as effective as when formalin is used

• Schaudinn solution contain mercuric chloride (mercury has potential health hazards)

sodium acetate formalin

advantages:

• only require single vial

• mercury-free

• easy to prepare

• long shelf life

sodium acetate formalin

disadvantages:

• adhesion properties not good, so addition of albumin to microscope slide may be necessary

• protozoa morphology is not as clear in permanent stains with mercury preservatives

modified polyvinyl alcohol

advantages:

• concentration methods and permanent stained smears

modified polyvinyl alcohol

disadvantages:

• do not provide the same quality of preservation for adequate protozoan morphology on a permanent stained slide as mercury-based fixative

• parasite identification will be more difficult

alternative single-vial systems

advantages:

• concentration techniques, permanents stained smear, fecal immunoassays

alternative single-vial systems

disadvantages:

• do not have the same quality of preservation as mercury-based fixatives, organism identification will be more difficult from permanent stained slides