Laboratory-based surveillance

Introduction

Laboratory-based surveillance is one of the pillars of infectious diseases epidemiological surveillance. Data collected and analyzed by laboratory-based surveillance systems include laboratory results from patients with infectious diseases that can be laboratory confirmed. These systems, along with notifiable diseases surveillance systems and sentinel primary health care systems, provide important epidemiological information for public health actions and for evaluating prevention and control measures. The existence of multiple surveillance systems allows each system to complement the other while it enables crossover conclusions drawn from the analysis of the information collected by each system separately.

Lab-based surveillance is used for a wide range of food-borne and waterborne diseases, blood-transmitted diseases, diseases that are transmitted through the respiratory system and zoonoses (Niesters, et al. 2013). The main aims of lab-based surveillance are: (i) assessing temporal trends in the frequency of detection of the pathogens under surveillance; (ii) detecting early pathogens with an increased probability of spreading; (iii) the detecting and confirming outbreaks, and (iv) strengthening other surveillance systems (Teutsch & Churchill 1994).

 

HCDCP Laboratory-based Surveillance System

The Laboratory-based Surveillance System (Lab-SS) of the Hellenic Center for Disease Control and Prevention (HCDCP) started operating in 1999 (with some modifications in 2004) with a small number of participating hospitals throughout the region, mainly in the Attica region. The evaluation of the system showed that data was incomplete and quality was low. To improve the system, and in the context of our country’s participation in European networks of laboratory-based surveillance, in September 2011 it was decided to re-organise the system. The pilot phase of the new Lab-SS started in February 2012 and has been coordinated by the Laboratory-based Epidemiological Surveillance Office of the Department of Epidemiological Surveillance and Intervention.

 

Pathogens under surveillance

The pathogens that are currently under surveillance through the HCDCP Lab-SS are the following: Salmonella spp. Shigella spp., STEC, Campylobacter spp., Yersinia enterocolitica, Giardia lamblia, Cryptosporidium parvum, Entamoeba histolytica, Streptococcus pneumoniae, Brucella spp., Legionella pneumophila, Rotavirus, Adenovirus, Norovirus, rubella virus, hepatitis A virus, measles virus and Toxoplasma gondii.

 

Surveillance sites

Potential surveillance sites are invited to participate in the Lab-SS and, upon acceptance of the invitation, HCDCP staff members visit the sites, which include hospitals, reference centers and diagnostic centers, and train health professionals in the implementation of the system.

So far, the sites that have participated in the system are the microbiology laboratories of eight public hospitals, one reference center and two branches of a large private diagnostic center. Other surveillance sites are gradually being added until the goal of a sufficient number of participating sites representative of the geographic and population distribution of the target population of the whole country is achieved.

 

Process – Evaluation

For the purpose of data collection, a special form of notification of laboratory results was designed. The form includes information on the number of positive test results for the pathogens under surveillance, information on serotypes, as well as basic demographic information of patients with specific positive test results. Data is collected on a weekly basis and recorded in an electronic database that was designed based on the notification form and created using the Epi-Info software of the USA Centre for Disease Control and Prevention. The data is then encrypted and sent via email to HCDCP headquarters where it is decrypted and checked for quality and completeness. This check initiates the necessary corrective actions after which the data is imported into the central HCDCP database for analysis.

The pilot phase of the Lab-SS involves continuous and regular evaluation and restructuring of the notification forms along with the necessary database changes. As a result of the evaluation process, there might be changes in the information flow to facilitate the unhindered participation of the surveillance sites and to improve the effectiveness of the surveillance.

 

Data analysis

Currently, statistical analysis focuses on descriptive statistics for the purpose of checking data quality. Once the goal of having a sufficient number of participating sites is achieved, the aim is to analyze the data on a weekly basis. The analysis will include: (a) time trends in the frequency of detection of the pathogens under surveillance, (b) geographical depiction of their frequency, (c) analysis by age, gender, nationality and other factors included in the notification forms.

Data from the current participating surveillance sites is available for a different number of epidemiological weeks due to different times of entry to the Lab-SS system. The absolute number of positive test results for the pathogens under surveillance from the four surveillance sites with the largest number of available epidemiological weeks is shown in Table 1. Figure 1 shows the relative frequency of positive test results of pathogens under surveillance that were detected by stool cultures in the four surveillance sites for a total of 52 epidemiological weeks (27th week of 2012–26th week of 2013, July 2, 2012–June 30, 2013).

 

Table 1. Absolute number of positive test results for the pathogens under laboratory surveillance from four surveillance sites for a total of 52   epidemiological weeks (27th week of 2012–26th week of 2013, July 2, 2012–June 30, 2013)

PATHOGEN

“P. & Α. KYRIAKOY”

GENERAL CHILDREN’S HOSPITAL

“AGIA SOFIA” CHILDREN’S HOSPITAL*

THESSALONIKI SPECIAL DISEASES’ HOSPITAL

BIOMEDICINE OF ATHENS

(VIOIATRIKI)

Stool culture

 

Salmonella spp.

43

38

54

10

Shigella spp.

14

26

1

0

STEC

0

0

0

Test not performed

Campylobacter spp.

19

75

121

18

Yersinia enterocolitica

9

1

1

0

Stool parasitological test Giardia lamblia

1

1

11

9

Cryptosporidium parvum

0

0

6

0

Entamoeba histolytica

0

0

8

0

Culture of clinical specimen Streptococcus pneumoniae

0

8

0

0

Brucella spp.

1

1

5

0

Detection of antigen in urine Legionella pneumophila

Test not performed

0

0

0

Detection of antigen in stool Rotavirus

66

227

152

6

Adenovirus

39

201

0

20

Norovirus

57

15**

0

0

Recent infection

antibodies

 

Rubella virus

0

1

1

2

Hepatitis A

10

20

4

0

Detection of IgM or PCR Τoxoplasma gondii***

1

0

4

0

 

 

*The data for the 26th week of 2013 (June 24–June 30) is not available for the “Agia Sofia” Children’s Hospital.

** The detection of Norovirus antigens in stool started to being performed in the “Agia Sofia” Children’s Hospital in January 2013.

***Detection of antibodies or PCR for Τoxoplasma gondii in specimens from infants <1 year\s

Figure 1. Relative frequency of positive test results for the pathogens under surveillance that were detected through stool culture for the four surveillance sites for a total of 52 epidemiological weeks (27th week of 2012–26th week of 2013, July 2, 2012–June 30, 2013)

 jan2014en_invited_1

 

Next steps

The ultimate aim of a laboratory-based surveillance system is to implement it in a sufficient number of sites so the collected data will depict the frequency of occurrence of the pathogens under surveillance in the target population of the whole country. Therefore, the implementation of the system is gradually being extended to additional surveillance sites. When the goal of a representative number of participating sites is achieved, the data will be analyzed on a regular basis and the results will be communicated in the form of a report to the surveillance sites and other involved agencies.

In addition, the range of pathogens under surveillance will be extended to accommodate the changing demands that arise in the field of public health as well as the requirements of the international surveillance systems. For example, in 2011 the European Centre for Disease Prevention and Control suggested a change in the hepatitis B and C case definition and notification of the chronic hepatitis cases in order to estimate the prevalence and the changes in the epidemiology of viral hepatitis.  The new European case definitions for hepatitis B and C to be used for the purposes of surveillance are based solely on laboratory criteria, which make it imperative to integrate hepatitis B and C viruses (and other immunological markers of the viruses) in the laboratory-based surveillance system. To accommodate this need, we structured a laboratory notification form for hepatitis B and C and we designed and built the respective electronic database in order to include hepatitis B and C viruses in the Lab-SS.

Another aim of the Lab-SS is to automate the procedure of collecting, sending, processing and analyzing the laboratory data. In this context, there was a NSRF proposal for the design and implementation of a web-based application for the entry, management, statistical analysis and geographical depiction of the data collected by the Lab-SS.

 

Conclusions

Surveillance systems of laboratory test results provide important epidemiological information for timely confirmation of infectious disease case occurrence or outbreaks and estimation of time trends in the frequency of detection of the pathogens under surveillance. The scientific and technological advances in diagnostic methods and the use of information systems require the synchronization of laboratory-based surveillance; automating the procedure of data collection and process allows not only greater flexibility and adaptation to the continuously changing public health needs, but also more efficient actions for the benefit of public health.

 

References
  1. Niesters, H.G., Rossen, J.W., van der Avoort, H., Baas, D., Benschop, K., Claas, E.C., Kroneman, A., van Maarseveen, N., Pas, S., van Pelt, W., Rahamat-Langendoen, J.C., Schuurman, R., Vennema, H., Verhoef, L., Wolthers, K., Koopmans, M., 2013. Laboratory-based surveillance in the molecular era: the TYPENED model, a joint data-sharing platform for clinical and public health laboratories. Euro Surveill, 18(4):pii=20387. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20387
  2. Teutsch, S.M. & Churchill, R.E., 1994. Principles and Practice of Public Health Surveillance, 2nd edn. Oxford University Press, New York, pp.18-9.

 

Angeliki Lambrou, RN, MPH, ScD, Laboratory-based Epidemiological Surveillance Office, HCDCP.
Ioanna Kokkali, Administrative officer, Laboratory-based Epidemiological Surveillance Office, HCDCP.
Nikolaos Bitsolas, Informaticist, Regional Public Health Laboratory of Thessaly.
 

The Laboratory-based Epidemiological Surveillance Office of HCDCP would like to express our deepest thanks to the personnel of the participating surveillance sites for their voluntary participation and valuable help in the laboratory-based surveillance. The list of the participating sites and the names of their personnel contact points follows:

SURVEILLANCE SITES Names
Biomedicine of Athens (Vioiatriki) Ioanna Dimopoulou
Biomedicine of Thessaloniki (Vioiatriki) Antreas Kampalonis

Dimitris Vasiloglou

Konstantinos Christoglou

National Reference Laboratory for Measles-Rubella, Hellenic Pasteur Institute Andreas Mentis

Elina Horefti

Kalamata General Hospital Erieta Vernardaki
Lamia General Hospital Dimitra Astrecha
Larissa General Hospital Ioanna Voulgaridi
“Agios Panteleimon” General Hospital of Nikaia, Piraeus Nikolaos Zachos
«Panagioti and Aglaias Kyriakou» General Children’s Hospital of Athens Nikoleta Palaiologou
Sparta General Hospital Dimitra Rempelou

Spuridon Fokas

Thessaloniki Special Diseases’ Hospital (NEPTH) Anthoula Kandili
“Agia Sofia” Children’s Hospital Kleopatra Kalogriopoulou