Article type
Year
Abstract
Background:
Surveillance studies are ranked low in the hierarchy of evidence, but there are conditions where randomized controlled trials cannot be performed and the available evidence is from surveillance. Surveillance for vaccine-preventable diseases is a form of evidence used by resource-poor economies to determine the disease burden and decide on policies for the introduction of specific vaccines. Though important, there are no definite rules to assess the quality of surveillance studies or to judge the biases in them.
Objectives:
To identify the problems faced in assessing the quality of surveillance studies while estimating the burden of vaccine-preventable diseases.
Methods:
Authors try to delineate the problems faced while assessing the quality and biases of surveillance studies for a systematic review on estimating invasive pneumococcal disease burden in children under five years of age. We considered the study setting, case definitions used, study population from which the samples were drawn - which also included age in months - and details on the use of antibiotics, type of samples drawn and laboratory methods used for isolation/detection of the causative agent.
Results:
Based on the above points it was discovered that 12 out of 21 studies identified differed significantly with regard to the standard case definitions, use of standard laboratory methods, age of surveyed population and type of sample used for isolation of the organism. This renders the results heterogeneous. Moreover the survey types and settings also differed; there were retrospective and prospective surveys done in hospital and community settings, thereby increasing the differences further.
Conclusions:
There is a need to formulate a concrete scoring system or bias assessment tool for surveillance studies so as to standardize the quality of surveillance studies.
Acknowledgements: Indian Council of Medical Research
Surveillance studies are ranked low in the hierarchy of evidence, but there are conditions where randomized controlled trials cannot be performed and the available evidence is from surveillance. Surveillance for vaccine-preventable diseases is a form of evidence used by resource-poor economies to determine the disease burden and decide on policies for the introduction of specific vaccines. Though important, there are no definite rules to assess the quality of surveillance studies or to judge the biases in them.
Objectives:
To identify the problems faced in assessing the quality of surveillance studies while estimating the burden of vaccine-preventable diseases.
Methods:
Authors try to delineate the problems faced while assessing the quality and biases of surveillance studies for a systematic review on estimating invasive pneumococcal disease burden in children under five years of age. We considered the study setting, case definitions used, study population from which the samples were drawn - which also included age in months - and details on the use of antibiotics, type of samples drawn and laboratory methods used for isolation/detection of the causative agent.
Results:
Based on the above points it was discovered that 12 out of 21 studies identified differed significantly with regard to the standard case definitions, use of standard laboratory methods, age of surveyed population and type of sample used for isolation of the organism. This renders the results heterogeneous. Moreover the survey types and settings also differed; there were retrospective and prospective surveys done in hospital and community settings, thereby increasing the differences further.
Conclusions:
There is a need to formulate a concrete scoring system or bias assessment tool for surveillance studies so as to standardize the quality of surveillance studies.
Acknowledgements: Indian Council of Medical Research