COPT

• Circumoval Precipitin Test (COPT)


  A form of serologic test based on the antigen-antibody reaction
• COPT Procedure


  1. Add 2 drops of patient's serum + lyophilized Schistosoma japonicum

  2. Cover with coverslip

  3. Seal with paraffin

  4. Incubate at 37°C or room temperature for 24-48 hours

  5. Examine under microscope
• COPT


  • Method of choice
  • Highly sensitive and specific for detecting Schistosomiasis, especially Schistosoma japonicum
  • Easy to perform
  • Superior test for detecting small amounts of Schistosomiasis
• COPT Disadvantages


  • Technically demanding
  • Not routinely used for field testing
  • Cannot detect active vs. past infection
• COPT Reagent


  • Around 100-150 eggs of Schistosoma japonicum ova with completely developed miracidium
  • Can stock for 3 years or longer
  • Stored in vials with desiccator at 4°C
• Kato-katz Result


  COPT Result
• ELISA


  • Highly sensitive and specific
  • Microwells are coated with Schistosoma recombinant antigen
  • Antibodies reactive to the antigen bind to the coated wells
• COPT is currently regarded as the method of choice for the definitive diagnosis of Schistosoma japonicum
• COPT


  • Sensitivity is due to the microprecipitation reaction visualized under the microscope
  • Sensitivity is comparable to passive or indirect hemagglutination
  • Positive Result: Bleb-like or septate precipitates/segments attached to egg surface
  • For Schistosoma japonicum infection, it may take more than 2 years for a negative result
  • Technically demanding and requires specialized equipment, not routinely used for field testing
  • Cannot distinguish between active and past infections
  • Used as an adjunct tool for diagnosis in patients who are stool negative but remain highly suspicious for schistosomiasis
• Materials Needed for COPT


  • Light microscope
  • Microscope glass slides
  • Glass coverslips
  • Pasteur pipette
  • Rubber bulb
  • Paraffin
  • Lyophilized Schistosoma japonicum eggs
• COPT Procedure


  1. Blood is extracted from the patient by venipuncture and the serum is collected

  2. 2 drops of serum are added to lyophilized S. japonicum eggs on a glass slide

  3. Mix the serum and eggs with the corner of the coverslip and place it on top

  4. Seal the sides of the coverslip with paraffin

  5. Incubate at 37°C (or at room temperature) for 24-48 hours before examination under the microscope

  6. A serum positive patient would produce bleb and/or segmented COP reactions

  7. Blood sample can be collected using the filter paper method