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Defining the Public Health Impact of Drug-Resistant Streptococcus pneumoniae - Report of a Working Group Appendix - Laboratory-Based Surveillance System


  1. Components and operation of the laboratory-based surveillance system

    1. Definitions

      The proposed surveillance system is intended to monitor only invasive pneumococcal infections and their antimicrobial susceptibility patterns. For this system, invasive pneumococcal infection refers only to meningitis and bacteremia identified by isolation of S. pneumoniae from cerebrospinal fluid (CSF) or blood, respectively. The system is not intended to monitor isolates obtained from respiratory secretions. Although information from respiratory isolates may be useful, the large number of sputum specimens routinely collected from patients who have pneumonia would likely overwhelm a surveillance system initially. Addition of surveillance for respiratory isolates might be considered in the future, depending upon ease of implementing surveillance, available resources, and expected utility. The following definitions have been approved by the Council of State and Territorial Epidemiologists (CSTE) for drug-resistant Streptococcus pneumoniae (DRSP) surveillance:

      1. Confirmed case

        A confirmed case of invasive DRSP is defined as either meningitis or bacteremia in which S. pneumoniae cultured from CSF or blood is identified as nonsusceptible (using National Committee for Clinical Laboratory Standards {NCCLS} methods and breakpoints) to antimicrobial drugs currently approved for treating pneumococcal infections.

        When oxacillin disk screening is the only antimicrobial susceptibility method used, the antimicrobial susceptibility profile cannot be definitely determined. For these instances, a probable case definition is needed.

      2. Probable case

        To obtain data from laboratories that perform only oxacillin screening, a probable case definition has been made. A probable case of invasive DRSP is defined as either meningitis or bacteremia in which S. pneumoniae cultured from CSF or blood is identified as nonsusceptible by oxacillin screening (i.e., zone size less than or equal to 19 mm) and no further antimicrobial susceptibility testing has been performed.

    2. Reporting

      Laboratories will be required to report probable or confirmed cases of DRSP to their state health departments in a line-listed manner to include the patient's date of birth or age, the anatomic site of specimen collection, the date of specimen collection, the antimicrobial susceptibility pattern, and unique identifiers for the laboratory and the specimen. The patient's first and last name also will be required at the state level; however, CDC will not have personal identifiers. Measures will be taken to protect sensitive health information. Current reporting software supports the capability to encrypt names, allowing personal identifiers to be removed. Having the encrypted name along with laboratory and specimen identifiers allows duplicate reports to be identified. To reduce duplicate reporting of isolates from the same episode of clinical illness, isolates from the same patient will not be added to the surveillance database if the specimen submission date is within 10 days of a previous report.

      To determine the incidence and prevalence of DRSP, the total number of invasive site isolates tested (i.e., denominator data) must be determined. Denominator data will be essential for providing relevant clinical information to physicians and other health-care providers (see Goal III, Objectives C and D). For laboratories with computerized data management, all invasive site isolates can be reported in the same manner as previously described. Laboratories unable to provide data easily in this manner should report aggregate denominator data monthly; data would include the total number of invasive site isolates tested by age group (less than 6 years of age, 6-17 years, and greater than or equal to 18 years of age) and anatomic collection site (i.e., CSF or blood).

      The data being collected for surveillance may be readily available from the computerized records of many laboratories. This information may be imported from laboratory computer files into a currently available standardized database format, which may be either transmitted electronically or sent by mailed diskette to the state health departments and subsequently to CDC. Ideally, computerized laboratories would be able to provide data output in Health Level Seven (HL7) standard format, or in a compatible standard format, for transmission to the state health department, where the data could be retrieved by compatible software. HL7 is being used increasingly as a standard for coding and electronically transmitting hospital and laboratory data, and its continued use as a standard should be encouraged by CDC, CSTE, and Association of State and Territorial Public Health Laboratory Directors (ASTPHLD). These HL7 standards and specifications should be made readily available to laboratory information systems (LIS) vendors and large national reference laboratories.

      Initially, the system would be piloted in selected cities. Ultimately, it is intended to be a comprehensive, population-based system for U.S. laboratories certified in accordance with the Clinical Laboratories Improvement Amendment (CLIA) of 1988, including hospital laboratories, commercial laboratories, and state public health laboratories.

    3. Data management and dissemination

      Data will be stored in three locations: the laboratory data repository, state health departments, and CDC. State-specific information regarding DRSP prevalence will be maintained at the respective state health departments and will be used to provide regular feedback of regional data to hospitals, laboratories, and clinicians (see Goal III, Objective C). Data merged from multiple laboratories will be periodically transmitted electronically to state health departments and CDC. These data will be compiled to determine DRSP prevalence data by state and to provide a quarterly national summary report (see Goal III, Objective D). State health departments will have the ability to restrict certain data fields, such as personal identifiers, before sending data to CDC. The quarterly results of the merged surveillance information will be published in journals accessible to laboratorians and clinicians. Data presented in a graphic format will reflect regional variations and temporal changes.

  2. Phases of implementation

The surveillance system will be implemented in four phases: pilot, addition of laboratories in the pilot community, expansion to other laboratories, and nationwide laboratory participation.

  1. Phase 1. Pilot study

    Two laboratories in New Jersey (one in Camden County and one in Middlesex County) have been identified for participation. These counties are the site of a vaccine demonstration study currently being conducted with CDC assistance. Both laboratories provide services to large academic centers and have agreed to participate in the pilot phase of the implementation of the surveillance system. These and other laboratories in New Jersey have been participating in surveillance of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococcus (VRE), and DRSP through a traditional surveillance mechanism that uses paper report forms. Implementing the pilot phase in New Jersey allows for introduction of electronic reporting in an environment where reporting is already required and familiar to laboratories.

    A review of the computer capabilities and laboratory practices of the two participating laboratories was performed in early January 1995. Initial site visits were made to introduce the hospitals to the electronic surveillance system. During a trial period after the initiation of the pilot, data will be collected and electronically transmitted to the state health department. Software will be available at the state level for analysis and for transmission to CDC. After the data are transmitted to CDC at the end of the first month of collection, the system will be evaluated and improved.

  2. Phase 2. Addition of laboratories in the pilot community

    In Phase 2, laboratories in the same counties as the two pilot laboratories will be added to the surveillance system. Phase 2 should begin approximately 90 days after initiation of Phase 1. Laboratories will be evaluated for participation in the following manner:

    1. Laboratory survey

      Through a mailed questionnaire, laboratories in the pilot area will be surveyed to determine the methods used for susceptibility testing of pneumococcal isolates and to determine the level of computer capability in the laboratory.

    2. Assessment of laboratories

      Laboratories capable of participation in the pilot should meet the following criteria:

      • Perform pneumococcal susceptibility testing by using NCCLS interpretive standards,

      • Enter and report laboratory data by using computers,

      • Have a laboratory software package capable of being translated to a database software through downloaded ASCII text, Health Level 7 standard format, or a comparable standard format,

      • Have a personal computer (at least a 386 processor) with a modem (greater than or equal to 2400 bps), capable of running PHLIS (Public Health Laboratory Information System) version 3.1, and

      • Have personnel available and willing to implement the pilot study.

        Laboratories meeting the criteria will be involved in Phase 2. Those laboratories not yet capable of electronic reporting will be encouraged to enhance their present system to participate in later phases. In the two pilot sites, 19 laboratories are expected to participate.

    3. Implementation and evaluation

      Data from the participating laboratories will be transmitted to the state health department at least once a month. At the end of each 30-day period, the state health department will transmit the data to CDC. The system will be evaluated and improved.

  3. Phase 3. Expansion of surveillance to other laboratories

    During Phase 3, laboratories in communities that have ongoing population-based pneumococcal studies will be enrolled. These studies may be CDC-sponsored emerging infections programs or other surveillance projects. Implementing surveillance in communities that have ongoing studies will enable comparisons to be made between the new, electronic, laboratory-based surveillance and the present standard for surveillance. Four to seven states are expected to have communities participating. When the surveillance is established within those communities with ongoing pneumococcal studies, expansion to include all laboratories within the state will begin. Implementation of Phase 3 is expected by late 1996.

  4. Phase 4. Nationwide laboratory participation

    Laboratories will be added to the surveillance system, with an estimated participation of 70% of clinical laboratories nationwide by 1998. Expansion of the surveillance system to include other laboratory-reportable illnesses is expected. The system proposed in the strategy is intended to utilize software and data transmission standards to allow coordination with other systems for reporting.

System attributes

The proposed surveillance system is intended to simplify data reporting by using information that is currently being collected in many laboratories. The system is flexible because the software used to manage and transmit the data will be able to accommodate other laboratory reportable diseases in the future. The system facilitates timely feedback to the laboratories and health departments because incidence of DRSP can be determined using the software both in the laboratory and in the health department.

IV. Utility

The surveillance system is intended to provide public health officials, clinicians, and health-care providers with data that can be used to prevent and control DRSP infections. In addition, the DRSP surveillance system is intended to be a model for the introduction of electronic, laboratory-based reporting of communicable diseases. Inherent in the implementation and maintenance of the surveillance system is the ability to change the components or the focus of surveillance to respond to results of new studies and emerging problems. Given the dynamic nature of DRSP, predicting the rate at which resistance to antimicrobial drugs will increase communitywide and nationwide is difficult. Surveillance may be scaled back and performed at selected sites when geographic and temporal variations in DRSP incidence are no longer apparent.

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