Communication between field epidemiologists & laboratory workers during outbreak investigations Dr. Gina Samaan Influenza Division – US CDC, Indonesia Office

Outline of Presentation o Importance of communication between from field epidemiologists and laboratory workers: 1.Choosing the right test. 2.Different tests – different results. 3.Comparison groups – expected results. o Lessons learnt and reminders for the future.

Hepatitis E Virus (HEV) Outbreak PICKING THE RIGHT TEST

A Waterborne Outbreak of Hepatitis E Virus Transmission in Southwestern Vietnam Am. J. Trop. Med. Hyg., 54(6), 1996, o In 1994, outbreak of hepatitis in southwest Vietnam. o One month after the outbreak, sera and epidemiological information were collected from 50 patients and 100 controls.

Laboratory Action o Specimen (10 mL blood sample) obtained from jaundiced outbreak cases/controls delivered by field staff to laboratory in HCMC. o Testing “FIRST” involved use of IgG Hepatitis A Virus (HAV) Assay. o IgG tests: evidence of recent or past infection o HAV identified as causative etiology.

Epidemiological Considerations o Over 90 percent of population in Mekong Delta Region exposed to HAV before the age of 12 years. o HAV has high case fatalities among pregnant women. o HAV has lengthy duration of illness.

Symptoms ALT IgG anti-HEV IgM anti-HEV Virus in stool Typical Serologic Course Titer Weeks after Exposure

Re-thinking laboratory approach based on epidemiological evidence o IgG HEV test kits obtained. o Specimens tested by lab: o IgM HAV Assay (evidence of acute infection). o IgG HEV Assay (evidence of recent/past infection). o Results: o <3% positive for IgM HAV. o 76% of cases positive for IgG HEV, and only 38% of controls (P<0.001). o Findings: o HEV identified as causative etiology.

Different tests - different results. Example from Dengue Outbreak in Indonesia

Epidemic dengue transmission in southern Sumatra, Indonesia. Trans R Soc Trop Med Hyg., 2001 May-Jun;95(3): o In 1998, outbreak of dengue. o 221 hospitalized patients had serum samples collected during the acute stage of illness. o From 221, 153 patients were positive for dengue.

Consider: Different test may gain or loose credibility depending on the time specimen collection. Different tests measure different immunological response. Three laboratory testing methods were used to confirm the 153 clinical cases of dengue:

CASE and Control Approach in Validating Laboratory Findings CASE and Control Approach in Validating Laboratory Findings Example From Leptospirosis Outbreak in Japan

A waterborne outbreak of leptospirosis among military personnel in Okinawa, Japan. In. J. Epidemiol Sep; 19(3): o In 1987, outbreak of leptospirosis amongst two groups swimming in the same river.

Perfect Outbreak from an Epidemiological Perspective o Two risk populations exposed to leptospira on the same river on same day: o CLUSTER 1: 82 marines in water training exercises. o CLUSTER 2: 15 recreational swimmers. o Clinical diagnosis of leptospirosis for 9 suspected cases at hospital: 4 from Cluster 1 and 5 from Cluster 2. o All found positive for leptospirosis by Perfecturate Okinawa laboratory using MAT. o Others from these risk populations also tested positive.

Too Perfect? o To validate laboratory findings, a Control Population of 14 people with no shared experience (no river swimming) were tested. o ALL tested positive at Perfecturate Okinawa Laboratory for leptospirosis by MAT!

Acting on Concerns o With validity of MAT findings in doubt based on Control findings, specimen sent to Regional Laboratory for MAT examination. o Leptospirosis identified as causative etiology: o Positives amongst cohort (exposed & sick) o Negative for all 14 controls.

Findings: Percent of people exhibiting leptospiral antibody and the geometric means titers by group GROUPSNo.% Positive (titre >200) % Positive (titre 1600) Geometric Mean Titre Suspected cases (sick) * Risk populations * Titre is signficantly greater (P<0.001) than for risk population.

Important to Remember: o Laboratory findings are a function of testing accuracy/validity & influenced by: –Training. –Equipment maintenance (including annual calibrations). –Reagent material (example: shelf life and expiration). –Procedures.

Quality assurance (QA) in the laboratory A program designed to produce sensitive, specific and clinically relevant laboratory test result. Ideally  includes everything from test selection & specimen collection to the final test result report. Basic elements: o personnel o space o equipment o standard of practice o reagents, stains, and media o proficiency testing

Responsibility of Epidemiologist o Communicate with lab regarding nature of specimen collection: sero-survey, clinical, or outbreak related. o Ensure the necessary field design that allows validation of lab findings: e.g. controls. o Ensure the “right” specimen (e.g. serum, stool, throat swab, etc). o Ensure specimens remain viable (e.g. transport media, temperature, etc). o Understand that Results can be influenced – and use your common sense. o Understand that different assays test for different immunological markers.

Ask Questions o What test will be conducted on this specimen? o Is it the correct test according to the clinical & epidemiological situation? o How should specimen be collected, stored & transported? o How do you interpret the test results? o What other tests should we consider? o Does this lab have good practices & quality assurance processes?

Examples from this Conference o Food poisoning outbreak in elementary school in Temanggung Regency, o Bacillus sp. in vomit but other pathogens found in suspected food source. o Hepatitis A outbreak in junior high school in Semarang, o Does epidemiology support Hepatitis A finding? Was testing done for Hep E? o Outbreak of clinical measles in Banyumas, o Are there differential diagnoses / etiologies for this outbreak?

Acknowledgements o Dr Andrew Corwin – for slide concepts. Thank you!