Week 4: Direct Fecal Smear

• The presence of parasites with intestinal in origin is primarily identified through direct examination of stool using wet mounts, concentration techniques, permanently stained smear, and culture

  
• Intestinal protozoan infections are diagnosed by the detection of trophozoites, cysts, or oocysts

  
• Routine methods for the identification of Ova and Parasites (O&P examination) should include procedures that permit the recovery of both protozoan and helminths

  
• Examination of three (3) specimens collected every other day is considered the minimum necessary to perform an adequate O&P evaluation
• For certain parasites such as G. lamblia and Strongyloides stercoralis, up to seven (7) O&P examinations must be performed for optimal detections

  
• Direct Fecal Smear


  Simple and rapid procedure for diagnosing common intestinal parasitic infection
• Direct Fecal Smear

  • Easy to prepare
  • Light infection may be misdiagnosed
• Examination of stool


  • Gross Examination
  • Microscopic Examination
  • Chemical Examination

  
• Specimen needed for stool examination

  Pea-sized specimen, approx. 3-5g of stool, collected in a clean, dry, waterproof, wide-mouth with a tight-fitting lid collection container
• Macroscopic Examination of stool

  • Color
  • Consistency
  • Presence or absence of proglottid or worm

  
• Microscopic Examination of stool

  • RBC
  • WBC
  • Bacteria
  • Fat globules
  • Parasites (Ova and parasites)

  
• Wet Smear Preparation


  1. Perform gross examination of the fresh stool sample

  2. Using a dropper, place a drop of Normal saline solution (NSS) on to the clean glass slide

  3. Get a pea-sized fresh stool sample from the stool container using an applicator stick. Gently emulsify the collected pea-sized stool sample in a rotary motion

  4. Cover the glass slide with a cover slip

  5. Observe the prepared slide under Low-power objective (LPO) and High-power objective (HPO) using a compound microscope

  
• Iodine Smear Preparation


  1. Using the wet smear prepared slide, gently drop Lugol's iodine at the edge of the cover slip

  2. Observe the prepared slide under Low-power objective (LPO) and High-power objective (HPO) using a compound microscope
• Lugol's iodine is used to visualize diagnostic characteristics of protozoan cysts

  
• This procedure is commonly known as fecalysis or stool examination