Simplicity, Data Quality, and Limited Resources: Evaluation of the Giardia Surveillance System in Maine

BACKGROUND:  Giardiasis is a highly infectious parasitic illness caused by the protozoan Giardia lamblia. Though rural with a small population, Maine had a significantly higher giardia incidence (16.8/100,000) than the US average (7.6/100,000) in 2010; it remains twice the national rate. The Maine Center for Disease Control and Prevention (ME CDC) centrally monitors giardia and other reportable diseases using the NEDSS Base System (NBS), an electronic surveillance system. With high volume and strained resources, ME CDC is concerned with the ability of its passive giardia system to maintain routine surveillance objectives as investigations are not performed. This assessment aims to identify system limitations and offer recommendations to improve its future use.

METHODS:  An evaluation was conducted for the period Maine NBS was used for giardia surveillance (2007-2013), following the Updated CDC Guidelines for Evaluating Public Health Surveillance Systems. Quantitative measures of data quality and timeliness were calculated using reports extracted from the Maine NBS. Data quality was assessed through completeness of reporting, and timeliness by measures of the duration between dates of specimen collection, report receipt, and entry. These attributes were evaluated along with system simplicity and acceptability through an operations analysis and qualitative stakeholder interviews.

RESULTS:  Data quality varies among the limited variables; missing elements range from 0.3 to 15.5% for four demographic fields, 0 to 1.0% for three investigative fields, and 0.3 to 12.7% for five reporting fields. The average difference from “earliest reported to state” to “case closing date” was 0.6 days (SD= 2.5; median= 0 days). Timeliness of case processing decreased from 97.4% entry within 2 days in 2010 to 89.9% in 2011, and 74.7% in 2012. Among other issues, ME CDC inadvertently failed to adopt the 2011 CSTE case definition change for giardia. Simplicity is excellent, as case ascertainment passes through minimal levels of reporting. Accordingly, acceptance by stakeholders is very good. However, the decline in entry priority and deviation from guidelines underscore the pitfalls of an overly-simple system.

CONCLUSIONS:  Limitations in epidemiologic capacity drive many small and rural health departments to settle on certain investigative priorities, creating the challenge of achieving surveillance goals without compromising data integrity. This evaluation has raised more issues than has provided answers, begging the question of how ME CDC can update the system to meet increased surveillance needs when faced with limited personnel and resources. The recommendations from this analysis will be tested and assessed in an ongoing evaluation.