Outline for a Case Study to Improve the Collaboration of Epidemiologists with Laboratory

Outline for a case study to improve the collaboration of epidemiologists with laboratory specialists

This outline describes the framework of a case study designed to improve the collaboration of trainees of Field Epidemiology Training Programmes (FETPs) with laboratory specialists. It was developed by the “salmonella working group” organized by the World Health Organization (WHO) Centre of Lyon, France.

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Part Introduction

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Use of the laboratory for surveillance and outbreak detection
Outline of the story / A reference centre receiving samples from many laboratories detects an increase number of isolates of Salmonella of a specific uncommon type (specify if it is a serotype, a phage typing or whatever else). This introduction section will contain epidemiological details regarding the time, place and person characteristics of this episode. / The National Centre for Cholera and Diarrheal Diseases in Calcutta, West Bengal receives stool sample from a large area in India. In September 2004, the number of stool from which vibrio cholera was isolated was 65, compared with a monthly average much lower between January and August.
Question asked / §  Describe the principles of the use of laboratories to detect outbreaks of unusual salmonella serotypes.
§  Would you describe this event as an outbreak? On what basis would you make that conclusion? / §  What is the role of the laboratory in public health surveillance?
§  How can these data be interpreted? Can this increase in the number of isolates be considered as an outbreak?
Response expected / §  Reference laboratories centralizing salmonella isolates for serotyping can detect trends that may suggest outbreaks. These trends could be difficult to detect using solely epidemiological methods (discuss examples of such systems and their use in specific clusters).
§  The increase in the number of isolates of one type of salmonella is suggestive of an outbreak since the occurrence of the event is more common than the baseline. It should lead to an epidemiological investigation. / §  Reference laboratories centralizing stool sample for cholera provides an indication of the epidemiological situation, but surveillance for acute diarrhea with dehydration among adults is the cornerstone of cholera surveillance.
§  West Bengal is endemic for cholera and has seasonal recrudescence in September and October. The increase in the number of isolates is probably a reflection of a large number of separate, localized outbreaks that should be investigated individually.
Appendices / resources to use / §  N/A / §  N/A
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Part Initiation of an epidemiological investigation

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Need of basic epidemiological data to initiate an investigation.
Outline of the story / On the basis of this increased number of one serotype, the surveillance system is activated to capture clusters of local salmonellosis cases. As an epidemiologist assigned to a local health department, you are notified that there is a cluster of febrile diarrhea in your district. This cluster could be part of this larger ongoing outbreak and needs to be investigated. / As a Field Epidemiology Training Programme scholar visiting NCED on (date), you hear about this increase in the number of isolates of vibrio cholera that reflects the annual time period during which the incidence of cholera is highest. As you return to your district, a colleague mentions a cluster of cases of acute watery diarrhea in a town. That cluster is suspected to be an outbreak of cholera.
Question asked / §  What are the initial steps of the epidemiological investigation in the field?
§  Should a microbiologist be in the investigation team in the field? In which circumstances would this be necessary?
Response expected / §  Set a case definition, look for cases, and collect basic line-listing information on the cases.
§  Nice to have a microbiologist in the field, but often not possible. What is important is to work together. / §  Confirm the occurrence of the outbreak, confirm the diagnosis, set up a case definition and look for cases.
§  Nice to have a microbiologist in the field, but often not possible. What is important is to work together.
Appendices / resources to use / §  Summary of the steps of an outbreak investigation / §  Summary of the steps of an outbreak investigation
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Part Collection of stool specimens

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Transport media to use and number of samples to take
Outline of the story / The investigation has been initiated and you have identified cases in the field. You are now about to collect specimen for laboratory investigations.
Question asked / §  How many case-patients should be sampled? Why?
§  What precautions should be taken when selecting the patients to be sampled?
§  What kind of samples should be taken? What quantity?
§  What is a transport medium? In which case should it be used? What kind of transport media should be used to take stool specimens in this case?
§  When is there a need for a cold chain for the transport of specimen? Why?
§  What other things need to be considered before collecting samples?
Response expected / §  Sample to take and quantity. Number of samples needs to be sufficient to avoid sampling error and small enough not to overwhelm the laboratory
§  Precautions for stool samples.
§  Rectal swabs for cholera.
§  A transport medium is a medium used to transport samples when it is expected that the samples will take some time before reaching the laboratory. Use of Cary Blair transport media for cholera.
§  Criteria for the need of the cold chain for the transport of specimen.
§  Making sure the lab is ready to receive samples.
Appendices / resources to use / §  N/A
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Part Labeling of stool specimens

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Minimum information that should be provided to the laboratory to ensure appropriate testing
Outline of the story / The samples have now been collected and are ready to be sent to the laboratory. While you are preparing to send the sample, your assistant asks you what kind of form he should use to send the samples to the laboratory.
Question asked / §  What kind of contacts should be made with the laboratory prior to sending the samples?
§  What kind of information should be made available to the laboratory with each sample to ensure appropriate laboratory testing?
Response expected / §  An initial contact with the laboratory will ensure that a contact person is identified (with phone number and email) so that they are aware of the episode, assign an outbreak number and ensure that someone will be available to handle the samples as they arrive (e.g., avoiding Friday afternoons and other difficult moments if possible).
§  Information required, including:
o  Confidential identifier for the case-patient, place and date
o  Type of sample
o  Date of onset, date of collection
o  Sign and symptoms of the patient
o  Prior antibiotic treatment if any
Appendices / resources to use / §  N/A
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Part Transport of stool specimen

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Safe sampling: Infection control, storage, transport
Outline of the story / As the samples are ready to go, you learn that the person who is supposed to carry them to the laboratory does not want to take them as he is afraid to catch the disease from it.
Question asked / §  What kind of infection control measures should be in place for the collection of stool samples?
§  What kind of package is necessary to prepare these samples for transport?
§  How should these samples be transported to the laboratory?
§  What can be said to reassure the person who will carry the samples?
Response expected / §  Recommended infection control procedures
§  Recommended package
§  Recommendations for the transport to the laboratory
§  Assurance that recommendations are being followed.
Appendices / resources to use / §  Biosafety slide set and guidelines
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Part Decision tree for laboratory testing

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Appropriate tests to request for a stool sample.
Outline of the story / The samples have now reached the laboratory safely. The microbiologist there calls you on the phone and thank you for all the information provided. However, he mentions that you did not specify what to look for and he wants to discuss that with you.
Question asked / §  In general, what kind of elements will be considered to decide the type(s) of laboratory tests to be done with a stool sample?
§  What kinds of tests are going to be requested to the laboratory in this particular case?
Response expected / §  Elements to use to decide the type of tests to be done with a stool sample
§  Test for salmonellosis and …[specify] / §  Elements to use to decide the type of tests to be done with a stool sample
§  Test for cholera and other main entero pathogens
Appendices / resources to use
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Part Quality assurance for laboratory testing

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Making sure the laboratory to which you are sending samples has quality assurance
Outline of the story / [Jaap to come up with an illustration of the QA issue for industrialized countries] / As you are getting input from an international colleague on this interesting outbreak, he gives you the advice that you should make sure that your samples are tested by a “good laboratory” that will provide reliable answers.
Question asked / [Jaap to come up with an illustration of the QA issue for industrialized countries] / §  What are the measures that a laboratory can take to improve the quality of the results and improve its reliability?
§  Can an epidemiologist assess whether a laboratory is reliable?
Response expected / [Jaap to come up with an illustration of the QA issue for industrialized countries] / §  Summary of quality control mechanisms
§  Limitations of the epidemiologist to assess the quality of a lab.
Appendices / resources to use / [Jaap to come up with an illustration of the QA issue for industrialized countries] / §  N/A
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Part Laboratory testing

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Types of laboratory techniques that may be used to identify
a pathogen responsible for an outbreak
Outline of the story / The samples are now being tested in the laboratory. Your assistant asks you what kinds of tests are going to be performed on them. Consideration is given to environmental sampling.
Question asked / §  At this stage of the epidemiological investigation, can one consider that the source of the outbreak is identified? Are additional epidemiological investigations needed?
§  What broad categories of laboratory techniques can a laboratory use to identify pathogens in a stool sample? What technique is the laboratory going to use in this case?
§  In general, what kind of laboratory tests can be conducted to assess the contamination of drinking water? What kind of tests could be conducted on the municipal water system in this case?
§  As the open sewage was suspected as a potential source of contamination for the municipal water system, would it be useful to also test samples from the sewage?
Response expected / §  Various types of laboratory techniques to identify pathogens: Antigen tests, cultures, nucleic acid detection…
§  Culture to request in this case.
§  Test to be used for environmental sampling
§  Relevance of environmental sampling
Appendices / resources to use / §  N/A
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Part Antibiotic resistance pattern

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Industrialized countries synopsis

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Developing countries synopsis

Topic covered / Relevance of antibiotic susceptibility testing during an outbreak investigation
Outline of the story / As salmonella was isolated from XX out of XX stool sample. No other pathogens were found. The laboratory is now calling to discuss with you whether an antibiotic susceptibility testing should be done. / As vibrio cholera el tor was isolated from 8 out of 10 stool samples. No other pathogens were found. The laboratory is now calling to discuss with you whether an antibiotic susceptibility testing should be done.
Question asked / §  How can the isolation of Vibrio cholerae O1 be interpreted in these samples? Why is it that other microorganisms were not found? What additional information are needed to interpret the negative results?
§  In general, what can be the usefulness of the antibiotic resistance patterns that should be received within 24 hours of the isolation?
§  What would be the relevance of antibiotic susceptibility testing in this specific outbreak? What kind of limitations should be borne in mind when interpreting antibiotic resistance patterns?
Response expected / §  Interpretation of the positive results.
§  Interpretation of the negative results. Need to know what was looked for.
§  First, antibiotic resistance patterns are used to guide treatment. In addition, they may be useful to monitor antibiotic susceptibility profile for surveillance purposes, and to some extend to type strains involved in outbreaks.
§  Antibiotic resistance patterns require quality assurance of the laboratory that handles the test.
§  [Find out what are the generally accepted criteria for the treatment of salmonellosis cases with antibiotics] / §  Interpretation of the positive results. Interpretation of the negative results. Need to know what was looked for.
§  First, antibiotic resistance patterns are used to guide treatment. In addition, they may be useful to monitor antibiotic susceptibility profile for surveillance purposes, and to some extend to type strains involved in outbreaks.
§  Antibiotic resistance patterns require quality assurance of the laboratory that handles the test.
§  During a cholera outbreak, it is useful to check for the antibiotic susceptibility profile of the strain involve to ensure that tetracyclin may be used to treat case-patients.
Appendices / resources to use / §  Reference to antibiotic treatment guidelines
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Part Typing, relevance of typing