Model Answers Microbiology Written examinations 2007 - RCPA
Model Answers Microbiology Written examinations 2007 - RCPA
Model Answers Microbiology Written examinations 2007 - RCPA
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General principles<br />
Routine vs selective<br />
The following factors should be taken into account when selecting a screening<br />
strategy:<br />
1. Detect infection<br />
Does the test detect potential foetal infection and damage?<br />
2. Assay<br />
Is there a sensitive and specific reliable assay available?<br />
3. Intervention<br />
Is there a safe and effective intervention strategy available if detected?<br />
4. Frequency<br />
Problems<br />
Does the infection occur at a frequency that has a cost benefit for the<br />
screening?<br />
Asymptomatic infections<br />
Poor positive predictive value<br />
Requiring further investigative actions<br />
Repeat serology/avidity etc<br />
Amniotic fluid examination<br />
Foetal blood examination<br />
Cord blood examination<br />
Often the true state of affairs remains unresolved<br />
Can generate angst for mother and family<br />
Termination as a result of not tolerating even minimal risk<br />
Psychological, Medicolegal, Ethical, Medical dilemmas<br />
Practical points<br />
Never base management decisions on a single test result<br />
Repeat tests preferably using a different method and on a second collection<br />
False positive IgM‟s are not that uncommon<br />
Serial sample testing important<br />
Avidity testing also may help – proportional to the maturation response of<br />
antibodies<br />
High avidity excludes infection in the previous 3- 4 months<br />
Low avidity usually BUT, not always, implies recent infection<br />
Stored serum samples at least for one year are important<br />
Examples<br />
Syphilis<br />
1. Detect potential foetal infection and damage
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