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tick bites jama complete.txt 48K ]
Tick Bites and Lyme Disease in an Endemic Setting
Problematic Use of Serologic Testing and Prophylactic Antibiotic Therapy
Alan D. Fix, MD, MS; G. Thomas Strickland, MD, PhD; John Grant, MD, MPH
Context.--The use of serologic testing to diagnose Lyme disease (LD)
is a source of controversy. Expert recommendations also discourage the
routine use of antibiotic therapy for prophylaxis of LD following tick
bites, but the extent to which physicians in endemic areas have adopted
these recommendations is not known.
Objective.--To assess the pattern of use of serologic testing and
antibiotic therapy for tick bites and LD and associated charges for
management in an endemic area.
Design.--Active surveillance of patient-physician encounters for tick
bites and LD.
Setting.--Primary care practices on the Eastern Shore of Maryland.
Patients.--Consecutive sample of 232 patients with tick bites, LD
(defined by physician diagnosis in medical record), and suspected LD
(physician notation of possible, but not definite LD) seen in 1995.
Main Outcome Measures.--Serologic testing for LD, test results,
antibiotic therapy, and direct costs of management.
Results.--Surveillance identified 142 patients (61.2%) with diagnoses
of tick bites, 40 patients (17.2%) with LD, and 50 patients (21.6%) with
suspected LD. Of the 142 patients seen for tick bites, 95 (67%)
underwent serologic testing for LD. Of these, 93 patients had initial
negative or equivocal results; 24 (26%) of the 93 had convalescent
testing, with 1 seroconversion. Seventy-eight patients (55%) with a
diagnosis of tick bite received antibiotic therapy. No patients with
tick bite developed clinical LD. Serologic testing for LD was performed
for 36 patients (90%) with a diagnosis of LD and 46 patients (92%) with
suspected LD. In most cases, antibiotics were prescribed before
serologic test results became available. Convalescent testing was not
performed for 37 (86%) of the 43 patients with suspected LD who had
initial negative or equivocal results. Of these 37 patients, 25 (68%)
did not receive antibiotic therapy. Direct charges for treatment of
these 232 patients totaled $47595, one third of which was attributable
to serologic testing. A total of 32% of direct charges were for
patients with tick bites, 48% were for patients with LD, and 20% were
for patients with suspected LD.
Conclusions.--In this setting, most patients consulting physicians for
tick bites received prophylactic antibiotic therapy of unproven efficacy
and underwent unnecessary, costly serologic testing. Despite almost
universal use in this study, serologic testing for LD did not appear to
influence treatment of patients diagnosed as having LD.
JAMA. 1998;279:206-210
------------------------------------------------------------------------
From the Department of Epidemiology and Preventive Medicine,
University of Maryland School of Medicine, Baltimore, Md (Drs Fix and
Strickland), and the Kent County Health Department, Chestertown, Md (Dr
Grant).
Reprints: Alan Fix, MD, MS, Department of Epidemiology and Preventive
Medicine, University of Maryland School of Medicine, 660 Redwood St,
SINCE ITS DESIGNATION as a nationally reportable disease in January
1991, Lyme disease (LD) has been by far the most commonly reported
vector-borne infectious disease in the United States.(1) It is
understandably a cause for much concern among physicians and patients in
endemic areas. In the absence of erythema migrans, the diagnosis of LD
is based on clinical criteria assisted by serologic testing in patients
with characteristic clinical manifestations.
The appropriate management of patients bitten by ticks in endemic
areas has proved problematic. Although most of the literature dealing
with management of tick bites does not recommend antibiotic
prophylaxis,(2-5) even in highly endemic areas, a large proportion of
practicing physicians prescribe antibiotics for tick bites.(6-8)
Further, the use of serologic testing in the management of LD has proved
a source of confusion and controversy(9-11) and has rarely been
discussed in the context of tick bites. Retrospective studies of the
clinical context in which serologic testing for LD has been performed
have called into question physicians' use of these tests.(12,13)
------------------------------------------------------------------------
For editorial comment see p 239.
------------------------------------------------------------------------
The Eastern Shore of Maryland is an area endemic for LD, having the
highest incidence in the state.(14) In 1995, the incidence rate of
reported LD in Kent County was 86 cases per 100,000 population and
varied in the 4 adjacent counties from 14 to 64 cases per 100,000
population.(15) We assessed patterns of use of serologic tests and
antibiotic therapy for tick bites and LD by physicians in this rural,
endemic setting.
METHODS
Patients prospectively identified with clinical diagnoses of tick
bites, LD, or suspected LD seen by primary care practitioners in Kent
County, Maryland, and within the Delmarva Health Plan (DHP) in the
adjacent 4-county area on the Eastern Shore of Maryland from January
through November 1995 were included in the study. Patients seeking
medical advice following tick bites, but without symptoms of LD, were
designated as having tick bite. Cases for which the physician recorded
a diagnosis of LD in the medical record were designated as having LD.
The data used to make the diagnoses were not evaluated. Patients with
LD noted in the medical record as a possible diagnosis, but not
considered by the physician as a definite diagnosis, were designated as
having suspected LD.
Arrangements were made with the offices of primary care practitioners
to keep a roster of all patients seen with LD, suspected LD, or tick
bites. The communicable disease surveillance nurses of the Kent County
Health Department visited offices in Kent County weekly to abstract data
from the medical records of patients appearing on the rosters. A nurse
made visits to the practices in the DHP periodically in response to
calls from the physicians' offices and/or receipt of computer lists from
the DHP of encounters for LD and insect bites, or of lists of those
undergoing serologic tests for LD, abstracting data from the medical
records of patients identified through these mechanisms.
The following information was extracted from the patient charts:
diagnosis, date of onset, dates and types of visits to the physician,
dates of diagnostic tests and their results, dates of procedures and
their results, dates of hospitalizations, and therapy prescribed.
Charges for physician and/or hospital visits, serologic tests,
procedures, and antibiotic therapy were ascertained. For patients
within DHP, all enzyme immunoassays (EIAs) were performed in the same
laboratory using the Lyme Stat Test Kit (Whittaker Bioproducts,
Walkersville, Md). Serologic test specimens for patients in Kent County
who were not members of DHP, in addition to being sent to the above
laboratory, were sent to several commercial laboratories, each of which
used a different kit. Western blot confirmation tests for LD were
performed in several commercial laboratories.
Since no patient identifiers were to be retained following the
collection of preexisting medical record information, this study
received an exemption from informed consent by the institutional review
boards of the University of Maryland at Baltimore and the Maryland
Department of Health and Mental Hygiene. Data were recorded and
analysis was performed using Epi Info, version 6.(16)
RESULTS
Of a total of 270 medical records reviewed, 232 patients with
diagnoses of tick bite, LD, and suspected LD were identified: 142
(61.2%) with tick bite, 40 (17.2%) with LD, and 50 (21.6%) with
Table 1.--Use of Serologic Testing and Antibiotic Therapy for Tick Bites
========================================================================
Antibiotic Therapy
|--------------------------|
No, Yes,
Serologic Testing No.(%) No.(%)* No.(%)*
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No 47(33.1?) 17(36.2) 30(63.8)
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Yes 95(66.9?) 47(49.5) 48(50.5)
----------------------------------------------------------------------
Negative result 91(95.8?) 46(50.5) 45(49.5)
----------------------------------------------------------------------
Equivocal result 1(1.0?) 0 1(100.0)
----------------------------------------------------------------------
Positive result 3(3.2?) 1(33.3) 2(66.7)
------------------------------------------------------------------------
Total 142 64(45.1) 78(54.9)
========================================================================
*Row percentage.
?Percentage of total.
?Percentage of those having serologic testing performed.
Table 2.--Convalescent Testing for Those With Negative or Equivocal
Acute Serologic Test Results and Antibiotic Treatment
==========================================================================
Initial Serologic No Convalescent Testing
Serologic Result Negative |----------------------|
Testing, or Equivocal, No Treatment,
...
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Tick Bites and Lyme Disease in an Endemic Setting