[LAB DIAGNOSIS] LAB MODULE 3 UNIT 2 AND 3 Flashcards
In surveys of infected population, as well as individual cases, it is sometimes desirable to estimate the intensity of infection by counting the number of eggs in the feces.
EGG COUNTING PROCEDURES
Egg counts provide a reasonable estimate of the number of adult worms present.
EGG COUNTING PROCEDURES
Egg counts before treatment may help determine whether treatment is needed and counts after treatment assess its success based on egg reduction rate (ERR) as a consequence of reduction of worm burden.
EGG COUNTING PROCEDURES
This procedure uses a measured amount of stool which has been sieved
through a wire mesh and pressed under cellophane paper soaked in glycerine-
malachite green solution.
A. Kato-Katz method
A uniform amount of stool is examined through the use of a template with a
uniform-sized hole in the middle.
A. Kato-Katz method
A hole of 6 mm on a 1.5 mm thick template will deliver (?)
41.7
mg of stool
o a hole of 9 mm on a 1.0 mm thick template, ?
50 mg
o a hole of 6.5 mm on a 0.5 mm thick template, ?
20 mg
All eggs seen in the whole preparation are counted.
A. Kato-Katz method
The total egg count is multiplied with a factor depending on the amount of
stool used.
A. Kato-Katz method
o The total number of eggs counted is multiplied by 24 for a
(1) template; by 20 for (2) template; and by 50 for
(3) template.
- 41.7 mg
- 50 mg
- 20 mg
Consistency of the stool is the main determinant for the sensitivity of this
technique, since well-formed stools yield higher egg counts than moist ones.
A. Kato-Katz method
The technique can only be done on fresh formed stools and not on liquid and
preserved samples.
A. Kato-Katz method
The only human nematodes for which it is reasonably possible to correlate egg
production with adult worm burdens are Ascaris lumbricoides, Trichuris
trichiura, and the hookworms, all of which are soil-transmitted helminths
(STH).
A. Kato-Katz method
Note: The procedure is also useful for assessing the intensity of infection with
Schistosoma.
A. Kato-Katz method
Owing to its simplicity and relatively low cost, the Kato-Katz technique is
recommended by the World Health Organization (WHO) for epidemiological
surveys and surveillance pertaining to soil-transmitted helminthiasis and
intestinal schistosomiasis control programs.
A. Kato-Katz method
uses a counting chamber with two compartments,
each with a grid etched onto the upper surface.
B. McMaster technique
This enables a known volume of fecal suspension (2 x 0.15 ml) to be examined
microscopically.
B. McMaster technique
A known weight, 2 gms, of feces and a known volume, 28 m l , of flotation fluid
are used to prepare the suspension with a total volume approximately 30 ml.
B. McMaster technique
When filled with a suspension of feces in flotation fluid, much of the debris will
sink while eggs float to the surface, where they can easily be seen and those
under the grid counted.
B. McMaster technique
The number of eggs per gram of feces (EPG) can be calculated by multiplying
the number of eggs under the marked areas by a simple conversion factor.
B. McMaster technique
Multiply the number of eggs counted in one compartment by 100, or by 50 if
both compartments are used, to give the number of eggs per gram (EPG) of
feces.
B. McMaster technique
has been developed to easily carry out the flotation of the fecal
sample (fresh or fixed) in a centrifuge, the translation of the apical portion of
the floating suspension, and the subsequent examination under the
microscope.
C. FLOTAC® and Mini-FLOTAC®
These techniques use the FLOTAC® apparatus, a cylindrical-shaped device
made of polycarbonate amorphous thermoplastic, with two 5-ml flotation
chambers, which allows up to 1 g of stool to be prepared for microscopic
analysis.
C. FLOTAC® and Mini-FLOTAC®