Principles of diagnostic tests and associated specimens. Clinical reports and sending isolates away for further identification.

  • Created by: RON_16
  • Created on: 07-03-21 20:21




DIRECT & CONCENTRATION - detecting OCP ( over cyst parasites ) for example Giardia intestinal cyst common in diarrhoea 

GRAM - positive or negative 

Fluorescence - used for confirmation and good for screening to detect microorganisms however we must be careful to check the whole slide as sometimes there may only be a few microorganisms present 

CELL COUNTS - count WBC and WBC especially for CFS samples is because the amount of CFS produced in the brain is small max less than 1 ML 

important in urgent, sterile fluids like CFS 

we count WBCS to see if the patient has an infection present ( as the count will be higher) and the type of WBC is important for treatment 

Neutrophil = nucleus of the cell has many lobes in nucleus & different in shape this will be higher in bacterial infections 

Lymphocytes = elevated in viral infections therefore the patient will not be treated straight away as the condition may be self-limiting 


 •Immunochromatography - lateral flow, quick, easy, inexpensive, POCT, liquid samples  we can use it for a pregnancy test, COVID-19, H. pylori  Take patients urine, blood or faeces and leave for 15 mins any line indicates +  control MUST be present or test is insignificant  low level of antibodies the red line cannot be seen and must use another test for confirmation  Latex antibody/antigen detection  confirm the presence of staphylococcus aureus  rapid & cheap results given in 1 min microbeads coated with an antibody specific to the bacteria  agglutination = +ve reaction  cross-reaction can occur and the difference between bacteria will not be known giving false positive results must ensure control is used or results are not controlled  ELISA-type techniques - detect the level of antibodies against viral infections  serum of blood samples put into machine  The darker the colour higher the level of antibody  the faint colour indicates a low antibody level  if it is specific it will link to antibody and enzyme will add to substrate changing the colour  STOP SOLUTION - ACIDIC TURNS COLOUR FROM BLUE TO YELLOW can detect Clostridium difficile which causes diarrhoea in elderly patients, HIV AND HEP B PCR - in infectious disease diagnosis, has resulted in an ability to diagnose early and treat appropriately diseases - sensitivity and specificity allow it as a rapid, efficient method of detecting, identifying, and quantifying organism. Multi-sticks  - URINE SAMPLES  - UTI INFECTION                                           


No comments have yet been made