Week 4: Direct Fecal Smear and Cellulose tape swab

• Direct Fecal Smear (DFS)


  Simple and rapid procedure for diagnosing common intestinal parasitic infection
• Fecalysis

  Stool examination
• Lugol's iodine


  Used to visualize diagnostic characteristics of protozoan cysts

  
• Examination of fecal specimen

  • Wet mounts
  • Concentration techniques
  • Permanently stained smear
  • 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


  • Advantage: Easy to prepare
  • Disadvantage: Light infection may be misdiagnosed
• 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)

  
• Manner of reporting macroscopic examination

  • Color: Indicate the color observed
  • Consistency: Indicate the consistency observed
• Manner of reporting microscopic examination

  • RBC: Average number per 10 HPF
  • WBC: Average number per 10 HPF
  • Bacteria: Rare, few, moderate, many per LPF
  • Fat Globules: Average number per 10 HPF
  • Parasite: No ova or parasite seen (NIPS) or identify the ova or parasite if observed

  
• Scotch Tape Swab Technique

  Also known as the Cellulose Tape Swab Technique/ Graham's Scotch Adhesive Tape swab; Gold standard for diagnosis of E. vermicularis
• Scotch Tape Swab Technique

  • A piece of transparent adhesive tape is pressed firmly against the perianal skin, and the adhesive surface of the tape is spread on a glass slide
  • The slide is then place under the microscope and observed for parasitic eggs
  • A drop of toluene or xylol may be placed between the tape and the slide to clear the preparation
  • The specimen should be collected 3 consecutive days at early in the morning before the patient has taken a bath or before the patient has washed the perineum; can also be obtained late at night 10-11pm when patient have already slept for several hours
  • At least 4-6 consecutive negative tapes are required to rule-out the infection
  • May also recover eggs of Taenia spp. And Schistosoma mansoni
• Principle of Scotch Tape Swab Technique

  Adult female Enterobius vermicularis migrates out of the anus at night and deposits her eggs over the perianal area. Eggs can be collected for examination using cellophane tape procedure for the recovery of the said worm. Pinworm eggs will adhere to the cellophane tape placed against the perianal folds.
• Scotch Tape Swab Procedure

  1. Apply a strip of transparent scotch tape 2 ½ to 3 inches in length to a glass slide so that the tape is wrapped around one end of the slide

  2. Obtain a sample, pull the folded tab so that the sticky side of the tape is freed, still leaving some of it stuck to the back of the slide

  3. Carry the freed tape over the end of the tongue depressor so that the sticky side is out

  4. Hold the tape and slide against the tongue depressor

  5. Press the sticky surface on to the right and left perianal folds but do not insert the blade into the rectum

  6. Replace the tape on to the slide. Pull tape back from the slide, leaving a small portion attached

  7. Add a drop of toluene and replace the tape on the slide. Toluene clears everything except the eggs and female adults under the LPO of the microscope

  8. Smooth out the tape with a piece of gauze which should be disinfected and discarded. Examine for the eggs and female adults under LPO
• Pinworm eggs are infectious, and specimens must be handled carefully to prevent infection. Always wear PPE such as gowns, gloves, and mask