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
LEARNING OBJECTIVES
- TYPE OF DIAGNOSTIC TESTS
Microscopy
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
RAPID
•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 …
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