Understanding of sentinel surveillance

Surveillance is a much talked topic in Public health course. This is an integral important part of in any health system for making it more responsive. However, we get muddled hearing number of terms that come with surveillance, especially when you are newbies to the surveillance system in health care. One of the frequently cited words among surveillance is sentinel surveillance. 

Surveillance is defined as “the ongoing, systematic collection, analysis, interpretation, and dissemination of data regarding a health-related event for use in public health action to reduce morbidity and mortality and to improve health”. Surveillance system keeps the track of any disease/conditions/risk factors and identifies any possibility of any outbreaks or epidemic early, helping to take steps for preparedness including early detection and treatment or management.

Surveillance can be categorised into Active Surveillance, Passive surveillance and Sentinel Surveillance, and disease specific surveillance. 

Sentinel Surveillance:

Case 1: BPKIHS,  is a sentinel surveillance center for Kalazar.

Why is it a Sentinel Surveillance center for Kalazar?

• It has commitment and willingness to remain as sentinel center for Kalazar
• It has all the laboratory diagnostic facilities to diagnose Kalazar
• It has skilled manpower doctors, nurses, paramedics required to manage/treat Kalazar cases
• It lies in Sunsari district, particular geographic area or population, and is near to the districts where the Kalazar is endemic 

What is it doing currently?

• It actively finds the cases in the community where kalazar is endemic: case detection
• It provides treatment for Kalazar and follow up
• (NOTE: BPKIHS could be sentinel surveillance centre for many other diseases)

With this example in background, we can clearly understand what sentinel surveillance is. It is a process of monitoring occurrence of particular conditions in a population or also a monitoring of disease occurrence in a specific cohort such as in a geographic area or population subgroup to estimate trends in a larger population. Always keep in mind that certain agencies are only selected as sentinel surveillance centre due to their capacities. 

Sentinel: a soldier or guard whose job is to stand and keep watch

Surveillance: close observation/monitoring

Like the way a soldier or guard is kept to monitor and check for anything for security in healthcare for certain diseases or risk factors, certain health centres are selected for surveillance of specified diseases and while doing so, that centre should meet all the prerequisites. 

Data collected in a well-designed sentinel system can be used to signal trends, identify outbreaks and monitor the burden of disease in a community, providing a rapid, economical alternative to other surveillance methods. Because sentinel surveillance is conducted only in selected locations, however, it may not be as effective for detecting rare diseases or diseases that occur outside the catchment areas of the sentinel sites.

1. Centers for Disease Control and Prevention. Updated guidelines for evaluating public health surveillance systems: recommendations from the guidelines working group. MMWR Morb Mortal Wkly Rep 2001;50(RR-13):2.

2. Sentinel surveillance. Immunization,vaccine and biologicals. http://www.who.int/immunization/monitoring_surveillance/burden/vpd/surveillance_type/sentinel/en/