Public Health Laboratory Practice and Disease Surveillance
Domain focus
Public health laboratory questions test notifiable disease reporting, case definitions, outbreak investigation, specimen referral and surveillance data quality in Cambodia's provincial and national system.
Core rules
- Use the national case definition before classifying a case; do not change it mid-outbreak without documenting the reason.
- Report notifiable diseases within the required timeframe to the health authority.
- An outbreak investigation proceeds through verification, case finding, descriptive analysis, hypothesis generation, analytical study and control.
- Laboratory confirmation supports but does not replace clinical and epidemiological case classification.
- Specimen referral requires triple packaging, cold chain and a completed request form.
Worked example
A village reports 12 dengue cases in one week among 600 residents. Attack rate = 12 / 600 x 100 = 2%. The reasoning: the denominator must be the population at risk, not the number of clinic attendees. Comparing this with the previous three-week average helps confirm an outbreak. The laboratory confirms cases with NS1 or IgM and reports line-list data without patient identifiers.
Traps
- Using clinic attendees as the denominator.
- Changing the case definition to make the numbers fit.
- Sending specimens without triple packaging.
- Reporting identifiable patient data in a surveillance summary.