Laboratory Testing for Tick-Borne Infections in a Large Northeastern Academic Medical Center

An 11-Year Experience

Joseph Rudolf, MD; Jason Baron, MD; John Branda, MD; Elizabeth Lee-Lewandrowski, PhD, MPH

Disclosures

Am J Clin Pathol. 2018;150(5):415-420. 

In This Article

Abstract and Introduction

Abstract

Objectives: We evaluated changes in the testing menu, volume, and positivity rates for tick-borne illnesses in a New England medical center over an 11-year time frame.

Methods: Testing data were obtained by a retrospective review utilizing searchable data from a laboratory information system archive.

Results: Testing for tick-borne infections (TBI) increased 5.3-fold over an 11-year time period and the number of positive test results increased threefold. Annual rates for Lyme serology positivity varied from 14% to 29% and for western blot confirmation from 26% to 48%. Test volumes and the number of positive results increased for all TBI endemic to our region.

Conclusions: Our results confirm national trends suggesting increasing rates of TBI and substantially increased testing. This may reflect a greater incidence of TBI in our region and/or increased awareness of these infections.

Introduction

Tick-borne infections (TBIs) are caused by a variety of bacterial, viral, and parasitic pathogens whose incidence varies across different regions of the United States.[1] In Massachusetts, the most commonly reported TBIs are Lyme disease, babesiosis, and anaplasmosis,[2] although infections caused by other agents (eg, Borrelia myamotoi, ehrlichiosis, tularemia) are observed less frequently. According to the Massachusetts Department of Public Health's most recent publicly reported surveillance data from 2014, there were 3,830 confirmed cases of Lyme disease and 1,770 probable cases in Massachusetts. Data on Lyme disease are not available from the Massachusetts Department of Public Health from January 1, 2015, to December 31, 2016. In 2016, there were 573 confirmed and probable cases of babesiosis and 828 confirmed and probable cases of anaplasmosis.[2] However, it has been long known that Lyme disease and some other TBI are significantly under-reported.[3] According to the Centers for Disease (CDC), the number of reported cases of Lyme disease has been steadily increasing over the past two decades.[4] Approximately 30,000 cases of Lyme disease are reported to the CDC in the United States each year.[1] Yet, a survey of laboratory testing results from seven large commercial reference laboratories using data from 2008 showed an estimated annual rate of Lyme disease of between 244,000 and 444,000, that is roughly 8 to 14.8 times the rate based on surveillance data of cases reported to the CDC.[5]

Testing for Lyme disease may include serology with western blot confirmation and in select cases (eg, Lyme arthritis) polymerase chain reaction (PCR). Testing for babesiosis includes thick and thin blood smear, serology, and PCR. Tests for anaplasmosis include serology and PCR. The availability of some of these tests has changed over time as reference laboratories have continually expanded their test offerings. In addition, tests for more recently identified TBI in North America, such as B miyamotoi infection, have become available. For these reasons, the menu of available clinical laboratory tests has evolved over the past decade, reflecting the development of new testing modalities and the introduction of tests for newly identified pathogens.

The Massachusetts General Hospital (MGH) is a large tertiary care academic medical center in Boston, Massachusetts, serving Boston and surrounding communities. Given its geographical location, a large number of patients with possible TBI are evaluated at the MGH. The clinical laboratories at the MGH provide testing in support of clinical care throughout the hospital and outpatient practices, including testing for TBI. Given the increased frequency of TBI reported both regionally and nationally, and the emergence of newly recognized TBI, the volume and complexity of testing for these infections would be expected to be increasing. In this study, we report an 11-year analysis of testing patterns for TBI in our hospital, including testing volumes, rates of positivity, and the changing patterns of testing modalities over time.

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