2. Surveillance
"sur" means "from above" and "veiller" means
"to watch
Surveillance is a systematic process of
collection, transmission, analysis and feedback
of public health data for decision making.
3. • It serves as an early warning system for
impending public health emergencies.
• It document the impact of an intervention, or
track progress towards specified goals
• Monitor and clarify the epidemiology of health
problems, to allow priorities to be set and to
inform public health policy and strategies.
http://www.who.int/topics/public_health_surveillance/en
4. 4
A dynamic vision of surveillance
Collect and
transmit
data
Analyze
data
Feedback
information
Make
decisions
All levels use
information
to make
decisions
Collect and
transmit
data
Analyze
data
Feedback
information
Make
decisions
All levels use
information
to make
decisions
5. Steps in establishing and maintaining surveillance system
Establish Goals
Develop Case definitions
Select appropriate personnel
Acquire tools and clearances for
collection , analysis and dissemination
Implement surveillance system
Evaluate surveillance activities
6. Purpose of Surveillance
1. Establish the baseline of a health condition
2. Understand trends and pattern of disease
3. Detect outbreaks or emergence of new disease
4. Estimate the magnitude of health problem
5. Identify resources needed during and after public health
emergencies
6. Evaluate public health programs and control measures
7. Determine nature and history of disease
8. Monitor changes in infectious agents
9. Set research priorities
10. Stimulate research
11. Inform research plan and implementation
12. Support public health program planning
13. Monitor changes in public health practice
Source: Adopted from Thacker sb,Berkelman RI. Public health Surveillance1998
8. WHO’s standard protocol for Surveillance:
• Is the case definition clear? appropriate?
consistent throughout the surveillance system?
• Is the reporting mechanism clear? Efficient? of
appropriate reporting periodicity? available to
all relevant persons and institutions?
• Is the analysis of data appropriate? susceptible
to proper presentation? used for decision-
making?
• Do the personnel involved have a good
understanding of the value of the surveillance
system?
Source: WHO Recommended Surveillance Standards WHO/CDS/CSR/ISR/99.2
9. Analysis of Surveillance Data
A. Time
• Graph over time
B. Place
• Map
C. Person
• Breakdown by age, sex or personal characteristics,
vaccination status
11. Types of Surveillance:
(a) A focused location for surveillance (such as health
facility-based surveillance or community based
surveillance).
(b) A designated or representative health facility or
reporting site for early warning of epidemic or
pandemic events (sentinel surveillance).
(c) Surveillance conducted at laboratories for detecting
events or trends not necessarily evident at other sites.
(d) Disease-specific surveillance involving activities
aimed at targeted health data for a specific disease.
(Disease surveillance and notifiable disease reporting
system)
WHO integrated disease surveillance and response in the African region a guide for establishing community based surveillance
Population based
13. Community based surveillance:
• Community-based Surveillance (CBS) is an active
process of community participation in detecting,
reporting, responding to and monitoring health
events in the community.
• The main reporters are community members who
detect and report cases that might be otherwise
not be reported to health care facilities
• To do this , community awareness campaign is
essential to carry out like educating them about
the signs and symptom of disease.
14. • Low and middle income countries often uses
CBS to track diseases
• It is conducted by volunteers who receive
training on health conditions from health care
worker or health care facilities to detect and
report suspected cases to the facility
• The scope of CBS is limited to systematic on-
going collection of data on events and diseases
using simplified case definitions and forms and
reporting to health facilities
15. How to establish community based
surveillance in its catchment area?
(a) Mapping the catchment area and
determining the number of CBS focal points
needed.
(b) Identifying community representatives
willing to be CBS focal points and accepted
by the community to play such a role.
(c) Training the focal points regarding the use
of case definitions and actions, and timelines
for reporting intervals.
(d) Defines a mechanism for regular feedback
and support to the CBS.
16. CBS should be a routine function for:
(a) Pre-epidemic period (to provide early
warning or alerts)
(b) Period during epidemic (to actively detect
and respond to cases and deaths)
(c) Post-epidemic period (to monitor progress
with disease control activities)
Integrated disease surveillance and response in the african region ; A guide for establishing community based surveillance
17. Advantages:
• To facilitate easy and early reporting, to keep
vigilance at the community level
• To get the community involved so they
understand their health problems.
• To help people to be free from diseases
• To improve the health of the people
• Detecting individuals who do not seek medical
care
• Building health care network within
community
18. Disadvantages
• Sensitivity and specificity of case detection
• Positive predictive value of the trigger events
• Timeliness of reporting and
• Acceptability of the system, based on
interviews of key informants in a sample of
villages.
• All Health conditions are not suitable for CBS
For eg STDs because of their associated social
pressure and consequences
19. Hospital based surveillance
• The main reporter in this surveillance system is
physician or any proper system placed in hospital
for regularly reporting and capturing information.
• The hospital may assign any physician or proper
system to take responsibility for such reporting
• This type of surveillance requires an accurate
estimation of the demographic characteristics of
the population under surveillance
• The hospital administration should be fully
informed and understand the importance of
surveillance.
20. Selection of surveillance population and
participating hospitals
• It should be demographically and
geographically well defined, and data should
be available on e.g. age distribution and
numbers of births and deaths
• The numbers of children in specific age groups
• Surveillance is best initiated in a population
that has been stable and is expected to best
able during the period of surveillance.
21. • A population that uses a single hospital or a small
number of hospitals and has good access to it or
them would be ideal. A study is easiest to conduct
if a single large hospital serves the population and
if the services it provides are free.
• It is advisable to be aware of the sources of health
care in the population under surveillance and the
numbers of patients they care for.
• Actual size of a surveillance population that
would yield accurate estimates is difficult to
determine, given the paucity of data on
hospitalizations in developing countries and the
unknown sensitivity of each system in detecting
and testing cases of gastroenteritis.
22. Advantages:
• Hospitalizations are easy to detect and they
have good source of well structured data
• Hospitalizations represent a significant cost in
health resources.
• Hospitals are likely to have a laboratory
capability
23. Disadvantages:
• Health conditions of mild illness as individual
does not seek health care or require
hospitalizations
• Some conditions which are not tracked well in
hospitals. (eg MI lead hospitalization could give
false estimate of true incidence)
• Lack of Representativeness of Reported Cases
• Lack of Timeliness
• Inconsistency of Case Definitions
• To get the denominator i.e. population at risk for
calculating the incidence
24. The final design of surveillance ought to differ
based on the context and challenges existing
locally, therefore requiring customizable and
adaptable strategies to ensure the feasibility
of caring out surveillance.
26. Active Surveillance
• Active surveillance (“hot pursuit”)identifies cases
through screening of hospital admission records,
emergency department logs, medical wards, and
intensive care units and out-of-hospital facilities,
including nursing homes, radiology centers, and
physicians’ offices.
• Screening is the essential step in active
surveillance
• Appropriate screening terms and rigorous
standardized procedures are necessary to
minimize the number of missing cases.
Source: Comparison of Active and Passive surveillance for CerebrovascularThe Brain Attack Surveillance in Corpus Christi (BASIC) Project
27. • The system does not wait for:
Case-patients to come to health care
facilities
Health care facilities to report cases
• Health care workers actively reach out to
detect cases
• Surveillance comes in addition to routine
health care delivery.
• This method requires more resources than
passive surveillance, but is especially useful
when it is important to identify all cases
28. When to consider active surveillance?
Informed decision based on vaccine
characteristics, pre-licensure data, safety
profile of similar vaccine/s, safety signal, other
• IS and rotavirus vaccines
• Limited pre-registration data
• Variation in vaccine characteristics –annual
changes to seasonal influenza vaccine
• To address vaccine safety ‘concerns’ that may/have
damaged confidence
• Active surveillance will include cohort and clinical
trails.
29. Advantages
• Can be very sensitive
• Can collect more detailed information
• May be more representative.
Disadvantages
• High Cost
• Labor intensive
• Difficult to sustain over time.
30. Methodology:
• It was double blind placebo controlled ,
Randomized clinical trail to evaluate the efficacy
of three doses of Rotavac against severe
gastroenteritis which was conducted at three sites
(Delhi , Pune and Vellore) in India between 2010
& 2013
Subject recruitment and follow up:
Subjects enrolled 6-7 weeks of age
Active Surveillance for IS in a phase 3 efficacy
trail of a oral monovalent rotavirus vaccines in
India - Jacob John
31. •The phase 3 clinical trail enrolled 6799 children
across three sites ( Delhi -3799, Pune -1500,
Vellore- 1500)
Vaccine(Rotavac) Arm -4419
Placebo Arm-2191
32. • Randomized in 2:1 ratio to receive 3 doses of
vaccine or a placebo.
• The first 1/3rd of the participants enrolled in
the study at all three sites were followed for
their safety (staff doing daily contacts for 14
days as follow up for vaccine)
• 2/3rd included in the trail were followed
weekly until the age of two years of follow up.
• Caregivers were given mobile phones and
access to the study team whenever the child
suffered from the symptoms of acute
gastroenteritis.
33. Screening and management of suspected IS:
•Screening criteria for suspected IS were
identified and treated appropriately
•Each children with IS were identified and
examined by the study team and was taken for
pediatric consultation and hospitalization if
required
•All diagnosis was confirmed through
Ultrasound screening
34. Adjunction of Cases:
•Independent Case adjunction committee blinded
to the children allocation to different groups
reviewed all clinical reports and radiologic
evidence of IS cases and brightons criteria of IS
•This committee constitutes senior pediatric
surgeon , pediatric radiologist and pediatrician.
•Relative risk was calculated for 7 day ,14 day
and 60 day periods after any dose and 365 day
period after first dose.
36. Results:
The incidence rate of confirmed IS among
vaccine group was 94/100,000 child years (95%
CI ,41,185) and 71/100,000 child years years
(95% CI ,15,206) in Placebo group.
No temporal association with vaccination
(including 2 year of follow up, the
difference between the treatment arm was
not statistically significant
OR ratio calculated 1.34
37. Limitations:
• Due to usage of broad criteria for identifying
cases in active surveillance resulted in
screening of children with non specific illness
were also have undergone ultrasound
screening
• This surveillance has also diagnosed large of
transient cases .
38. Passive Surveillance
• Passive surveillance(or “cold pursuit” )ascertains
cases by searching hospital discharge diagnoses.
• Health care facilities or providers report cases as
they present in health care facilities
• No specific efforts are made to make sure all
cases are reported
• Surveillance is integrated to routine health care
delivery
• Cases are identified as per case definition
39. Strengths
• Large population cover
• Simple to operate/inexpensive
• Signal detection
• Hypothesis generation
• Triggers further investigation
• Cost
• Easier to design and carry out
• Useful for monitoring trends over time
40. Weaknesses
• Reporting biases –Under-reporting
• Stimulated reporting
• Inconsistent data quality/completeness
• Can’t determine AEFI incidence
• Not designed to assess causality
• Low sensitivity
• Amount of data available is limited
• May not be representative
41. Methodology: Retrospectively the medical
record of confirmed cases of IS in children under
age of five , treated during 2007-2012 at two
tertiary care hospitals(KMC and CSM Medical
university)
1. Study area and participating hospital: were
finalized for the surveillance site
Retrospective surveillance for IS in children
aged less than five years at two tertiary care
centers in India
- -J.V. Singh
42. 2. Case definition and data sources:
• Screening criteria to identify cases were
determined for five complete years .
• Inclusion criteria: Child<60 months of age with
confirmed diagnosis of IS, using the case
definition of Brighton collaboration
3. Data collection and analysis:
• The data was pooled and analyzed according to
age , sex, clinical signs, year and month of
hospitalization ,diagnostics and treatment
related characteristics
43. • The most common diagnostic methods used
were Ultrasonography and abdominal
radiography with most cases being treated
surgically (71%). The median length of
hospital stay was 8 days (range 1-40) and
mean was 10.2 days. Records of any fatality
due to intussusception were not found during
the review of the records.
44. Results:
• Over a five to six year observation period 187
confirmed cases of intussusception , were
identified , of which 75% were males. The
median age of intussusception was 8 months,
and most of the cases presented were below 12
months
• A possible trend in the distribution of cases
with the highest number of cases being
reported in the month of April and lowest in
the month of October.
45. Limitations
• Lack of complete data on immunization
• Inability to define the catchment area
• Tertiary care referral centers were selected ,so
might be most severe cases were covered.
46. Stimulated passive surveillance
• Health care facilities or providers report cases
as they present in health care facilities
• Special efforts made to maximize reporting
through reminders, visits
• Surveillance remains integrated to routine
health care delivery
47. Methodology:
•Surveillance of IS presenting in first year of life ,
within the period of 1st March 2008 & 31st March 2009
•BPSU was used in collaboration with BAPS
• Criteria for screening was established which
included:
Infants admitted with suspected or confirmed
cases of IS during the study period in NHS and
equivalent hospitals across UK and republic of
Ireland.
Prospective Surveillance study of the
management of IS in UK and Irish infants
- Lamiya Samad
48. Cases were classified according to
Brighton's collaboration criteria as Definite
(level1), Probable (level 2) or Possible (level
3).
• BPSU cards were sent to pediatric surgeons
and pediatricians to notify the cases of IS
meeting the case definition criteria
• Clinicians were then contacted with brief study
questionnaire on the epidemiology and clinical
features of IS
• Study response rate was calculated
• Duplication of cases identified
49. • Cases were then classified according to
internationally agreed and validated BCC
• Incidence rate was calculates using number of
definite cases as numerator and total number
of live birth ( from the office of national
health statistics by linking birth and death by
using NHS numbers in the cohort of babies
born in 2008 )
51. • The base line rate of incidence of
intussusception prior to the introduction of
rotavirus vaccine into UK vaccine schedule
was calculated.
• Baseline rates obtained for UK 24.8/100,000 &
Republic of Ireland 24.2/100,000
52. Limitations
• Only definite cases of intussusception was
included so may cause underreporting so there
may be underestimation of actual cases of IS
• It rely lot on clinical interest and involvement
so consistency and adherence to the study
protocol and validation is important
53. Active & Passive surveillance
(Integrated surveillance)
• A combination of active and passive systems using
a single infrastructure that gathers information
about multiple diseases or behaviors of interest to
several intervention programs.
• It require coordination and collaboration among
various programs, first line providers (veterinarians
or clinicians), epidemiologists, information system
specialists and laboratory personnel, design efforts
must consider each of these groups’ needs,
capabilities, limitations, logistical assets, budgetary
realities and legal requirements.
54. • In this study surveillance sites were identified
then retrospective view of all children was
taken. Hospital records of children 0-2 years of
age with intussusception treated between Jan
2010 to 31st Aug 2014 were undertaken at CMC
Vellore .This hospital caters to 1.9 million
outpatient and 120,000 inpatient annually
• 61 cases cases of intussusception in children
under two year were presented in hospital
Intussusception in southern India: Comparison of
retrospective analysis and retrospective surveillance
-Susan Jahangir
55. • Retrospective study
Cases were identified in two steps:
Ist step : Possible cases of IS were identified
through electronic search of the radiology
database and operation registers.
2nd step: the diagnosis of IS is then confirmed
by reviewing medical records , operation notes
and other investigations
• The study demonstrates IS identified through
active surveillance and those retrospective
surveillance differ in presentation , severity of
illness, need for intervention and outcome.
56. • Active surveillance in a vaccine trail was done
(N=1500) they were randomized in 2:1
• 16 cases of ultrasound diagnosed IS were identified
through active surveillance of cohort of 1500
children participating in rotavirus phase three trail.
• In active surveillance all participants were given
mobile phones and access to call centre around the
clock for the duration of follow up. Any child
having the history of symptoms of IS were
contacted to minimize the risk of developing IS .
• Suspected case was reviewed by pediatrician and
those having even transient IS were reviewed by
pediatric surgeon
57. Results IS presenting through routine care identified on
retrospective analysis (Passive surveillance)
• 61 cases were identified
• The median time of onset and arrival to hospital was 48h.
• The median age at presentation was 214 days with 52 events
occurring in first peak of life
IS identified through active surveillance and referral of a
vaccine trail cohort (Active surveillance)
• 16 cases of IS were diagnosed out of which 7 meet the
level 1 criteria
• 6 met the level 2 criteria
• 3 met the level 3 diagnostic criteria
• 8 cases of IS Occurred in first year of life
• 16/444 positive ultra sonograms
58. Limitations
• As the data collected were from referral hospitals:
So the cases covered were the most serious cases
and therefore generalizability issues exists.
• Inability to define the catchment area for IS: cases
or to have the birth cohort data for the catchment
population under study
• Lack of complete immunization data: It was
difficult to identify the exact number and type of
immunization administered prior to
hospitalization for IS
59. Sentinel Surveillance
Choose key “location” to monitor for condition
of interest. “Locations” might include
• Sites
• Events
• Providers
• Animals/Vectors
• Choose a “location” that is most susceptible to
change.
60. The following criteria should be considered in
selecting a sentinel health facility (usually a
general or infectious disease hospital) :
• It should be willing to participate.
• It serves a relatively large population that has
easy access to it.
• It has medical staff sufficiently specialized to
diagnose, treat and report cases of the disease
under surveillance.
• It has a high-quality diagnostic laboratory.
Source:http://www.who.int/immunization/monitoring_surveillance/burden/vpd/surveillance_type/sentin
el/en
61. • Sentinel surveillance system is used when high-
quality data are needed about a particular disease
that cannot be obtained through a passive system.
• Selected reporting units, with a high probability
of seeing cases of the disease in question, good
laboratory facilities and experienced well-
qualified staff, identify and notify on certain
diseases.
• Whereas most passive surveillance systems
receive data from as many health workers or
health facilities as possible, a sentinel system
deliberately involves only a limited network of
carefully selected reporting sites.
62. • For example, a network of large hospitals might be
used to collect high-quality data on various diseases
and their causative organisms, such as invasive
bacterial disease caused by Haemophilus influenzae
type b, meningococcus or pneumococcus
• The success of this approach lies in execution of a
system-wide design process that fosters
communication and collaboration amongst the
multiple stakeholders operating within a
surveillance system, two elements that are pivotal
for building effective and agile coordinated national
response to local and international public health
emergencies.
63. Disadvantage:
• If the site is not selected properly, data may
not be representative of general population ,
thereby proving inadequate estimates of
incidence and prevalence.
64. Incidence of intussusceptions in Singaporean children
aged less than 2 years: a hospital based prospective study
-Kong Boo Phua
• This was prospective, hospital-based, multi-centre
surveillance study was conducted in hospital
• All children aged < 2 years and admitted to the study
hospitals with a diagnosis of IS–categorized as definite
(ascertained by: radiograph, surgery or by post-mortem
examination), probable, possible or suspected cases
based on the criteria developed by the Brighton
Collaboration Working Group were enrolled.
• Data on IS were obtained from the daily admission
logs, computerized hospital admission records,
emergency department records, surgical records and
radiology logs etc
65. • All departments that were responsible for the
management of IS cases were advised to
contact the study personnel for each case of IS
to ensure that all cases were captured
• Annual Incidence of IS
= Number of new IS cases reported in a specific year*100,000
The total number of children living in Singapore during the specific year
66. Results:
• Of the 178 children assessed, 167 children with
definite IS cases were considered for final
analyses; 11 were excluded (six diagnosed as
probable IS and four diagnosed as suspected IS;
one child’s parents withdrew consent).
• The overall incidence of IS was 28.9 (95% CI:
23.0–34.8) and 26.1 (95% CI: 22.2–30.0) per
100,000 child-year in children < 1 year and <
2 years of age, respectively. The majority of IS
cases (20 [12.0%]) were reported in children aged
6 months.
68. Prospective Study - looks forward, looks to
the future, examines future events, follows a
condition, concern or disease into the future
Study begins here
Time
69. Retrospective Study - “to look back”, looks
back in time to study events that have already
occurred
Time
Study begins here
70. 1. Cohort Design:
• A cohort is any group of people who are linked
in some way and followed over time.
• This group is then compared to a similar group
that hasn't been exposed to the variable.
• Researchers observe what happens to one
group that's been exposed to a particular
variable — for example, Infants who were
vaccinated or non vaccinated whether they
develop the disease outcome.
71. • Follows two or more similar groups that differ
with respect to whether they received a
vaccine (the “exposure”) to determine
how/whether the vaccination affects rates of
one or more AEs (the “outcome”)
72. Source: centre for disease control; Vaccine for children program
Cohort Study Design
74. Strengths:
• Exposure status determined before disease
detection
• Subjects selected before disease detection
• Can study several outcomes for each exposure
Limitations:
• Expensive and time-consuming
• Inefficient for rare diseases or diseases with
long latency
• Loss to follow-up
75. 2. Self controlled case series design:
• Simple method that uses data on case patients
alone (i.e. without external Control group)
• To assess safety or risk exists in defined time
intervals after vaccinations.
• SCCS method compares the Relative incidence of
IS within the risk window of interest with the
incidence of risk outside the window of interest.
• Robust and cost efficient approach and can be
applied in resource poor settings or baseline
disease surveillance before vaccine introduction
76. The major features of SCCS are that
(1) it automatically controls for time-fixed
covariates that don’t vary within a person during
the study period, and
(2) only cases (individuals with at least one event)
need to be included in the analysis.
• It includes only individuals who experienced
the AE. Each individual serves as his or her own
control. The analysis inherently controls for
covariates that remain stable during the study
period—for example, race and sex.
• SCCSs compare outcome event rates both post
vaccination and prevaccination to calculate the
relative incidence of AEs
77. Self control case series study Design
2 3 4 5 6 7
8
Vaccination
“Risk”
Window
Period outside the risk window(“Control”)
78. • Potential time fixed confounders are of lesser
concern in contrast to traditional case control
method as only case data is being used.
• The self-controlled case series (SCCS) represents
one particular methodology that may be useful for
active surveillance of drug safety.
• SCCS has strengths and weaknesses.
Modifications of the basic model can address
some but not all of the weaknesses.
Further research is required to establish the
operating characteristics of SCCS-based
active surveillance.
79. Limitations:
• As SCCS estimates the exposure-outcome
association in cases, it ignores data on
individuals in the study population that did not
experience the outcome event.
• SCCS approach concern the underlying
independence assumptions, in particular, the
assumption that events are conditionally
independent, and the assumption that the
exposure distribution and the observation
period must be independent of event times.
80. Methodology:
• Self-controlled case series is used by extracting
intussusception cases in infants <12 month age from
hospital databases (2005-2012) and with vaccination
histories from a national immunization registry.
• Relative incidences were calculated by comparing
incidence during defined risk periods after vaccination
with times outside these periods.
Risk Period: 1-7 days and 8-21 days after vaccination
with day 0 being the day of vaccination.
Non-risk period : time period before vaccination and
>21 days after a dose of rotavirus vaccine, within the 1-
to 12-month age observation period.
Intussusception and monovalent rotavirus vaccination
in Singapore Self-Controlled Case Series and Risk-
Benefit Study
- Chee-Fu Yung
81. Results:
Effect of vaccination program at 20% or 90%
coverage , compared with no program on
hospitalization attributable to rotavirus vaccination
Attributable to rotavirus IS in Singapore children,5
years old
82. Intussusception risk after rotavirus
vaccination in U.S. Infants W. Katherine Yih
Methodology:
Study Population: Children of age 5-36.9 wks to cover
recommended vaccination ages (2, 4, 6 months) plus
follow-up time and they were member of mini sentinel
data partners, Aetna, Health core and Humana between
Jan 2004 and Sep 2011.
• Cohort and self controlled case series were adopted
• Two risk intervals were specified for Rota Teq and
Rotarix i.e. 1-7 days and 1-21 days
• Medical records were reviewed to validate the vaccine
exposures and type of rotavirus vaccination
83. Cohort Design:
•1-21 Days- Exposed person time after
rotavirus vaccination.
•5-36 wks of age from unvaccinated infants
and before and after 0-21 Days of
rotavirus vaccination.
•Data from the study population itself is
used for the age adjustment
84. Self Controlled case interval design:
Risk interval ( or Windows) : 1-7 and 1-21 Days
Control interval : 22-42 Days
Adjusted for age using the age-specific incidence
curve from Tate et al. and a randomization
method (As incidence rate of IS varies by week
of age)
89. Conclusion
• Evidence of association between IS and Rota Teq
was found which was highest in 3-7 days of first
dose.
• Evidence of association between IS and Rota rix
was also found which existed after second dose
• Relative Risk
Rota Teq -1.12( 95% CI :0.33-2.70) excess cases
per 100,000 (7 days after vaccination)
Rotarix- 1.54 (95% CI : 0.19-3.22) excess cases
per 100,000 (21 days after vaccination)
90. 3.Case Control study Design:
•Compares people who have a disease or
adverse event with people who do not
and compares exposure to vaccine in each
group to determine the relationship
between the vaccine and the
disease/event.
92. Strengths
• Less expensive and time consuming
• Efficient for studying rare diseases
Limitations
• Inappropriate when disease outcome for a
specific exposure is not known at start of study
• Exposure measurements taken after disease
occurrence
• Disease status can influence selection of
subjects
93. Methodology:
Population based Surveillance for IS (Dec
2000-Nov 2002)
Passive surveillance for hospitalized infants(
age< 1years) with IS was conducted in two
phases in south Delhi.
Age and sex specific estimates were used to
calculate the incidence of IS
Population-Based Incidence of Intussusception and a Case-
Control Study to Examine the Association of Intussusception
with Natural Rotavirus Infection among Indian Children
-Rajiv Bahl
94. The result obtained through passive
surveillance were linked with active hospital
based surveillance
Case control study of the association between
Rotavirus infection and Intussusception
Case selection: Infants irrespective of area
their area of residence were included for cases
(age 2-12 months ) who had a confirmed
diagnosis of IS by either Ultrasonography or
surgery
95. Control selection:
Infants (2-12 months of age) admitted to the
same hospital as the case patients but do not
have the IS
Assessment of case patients and control
subjects through questionaire
96. Active Surveillance:
•The community in south Delhi was selected of
population ~500,000
•Trained field worker conducted baseline house
to house survey to record the age and sex of
children ,5 years of age
•Total of 11,416 children were identified and
their age and sex specific estimates were used
as denominator for calculating the incidence of
IS
97. Results:
• Intussusception rates obtained ~ 18 cases per
100,000 infant years of follow up
• Patients with IS were assessed through
ultrasound reported that Rotavirus infection
was associated with increased distal wall
thickness and lymphadenopathy during illness
suggesting a plausible mechanism by which
rotavirus infection could cause IS
98. Limitations
• All patients in source population were not
covered because they either had died without
seeking medical care at hospital or have not
accessed it
• Less number of patients were included in the
study
99. Case cross over
• Study of “triggers” within an individual
• ”Case" and "control" component, but information
of both components will come from the same
individual
• ”Case component" = hazard period which is the
time period right before the disease or event onset
• ”Control component" = control period which is a
specified time interval other than the hazard
period
100. • This design was introduced to avoid control
selection bias.
• Case serves as it own control and it is similar
to retrospective cross over design except that
the investigator does not control when a
patient starts and stops being exposed to the
potential trigger.
102. • A case-crossover design was used. Cases of children
were the children admitted with a diagnosis of
intussusception hospitals in the city of Valencia, Spain,
from 2006 to 2009 (95 cases were selected< 2 years of
age)
• The association between the episode of intussusception
and the intake of prescription medication was assessed.
Case period :2, 7, and 15 days (before episode of IS)
Control period :for the same time window 1, 2, 3, and 4
months (prior to the episode of IS)
Association Between Medication and Intestinal
Intussusception in Children: A Case-Crossover Study
-Vega Garcia, Lourdes
103. Results:
• The association between the appearance of
intussusception in children and medication intake
in the immediately preceding period (2–15 days)
was assessed
• The association between intussusception and
prior drug use varied depending on the exposure
window:
15-day odds ratio (OR),1.45 (95% CI,0.86–2.43)
7-day OR, 1.46 (95% CI, 0.80–2.67)
2-day OR, 2.26 (95% CI, 1.10–4.64
