Journal of Clinical Microbiology, June 1999, p. 2118-2119, Vol. 37, No. 6
0095-1137/99/$04.00+0
LETTERS TO THE EDITOR
Treatment Strategies for Group A Streptococcal Pharyngitis
 |
LETTER |
In the recent, nicely done study by Needham et al. (2)
concerning the impact of a rapid group A streptococcal antigen assay on
physician usage of appropriate antibiotics, there are two areas of concern.
(i) In the abstract, the authors state that if the rapid antigen test
alone had guided therapeutic choice, an appropriate course of
antibiotics would have been prescribed for 95% of the patients during
the initial visit. In their conclusion, last paragraph, the authors
further state that neither the clinical assessment of the patients by
their physicians nor culture added significantly to the improved
outcome (i.e., appropriately using or withholding antibiotics) and that
the preferred strategy was exclusive reliance on the rapid antigen
test. While it is true that 95% of the total number of
culture-positive and -negative patients would have been appropriately
treated or not treated if the decision to treat had been based solely
on antigen assay results, 15 (12.9%) of their 116 culture-positive
patients (the target population for the diagnostic
tests) would not have been treated if
this strategy had been followed because their antigen test results were
falsely negative. This is an unacceptably high rate of diagnostic
failures and treatment errors.
In order to prevent the suppurative and nonsuppurative streptococcal
sequelae mentioned in the work by Needham et al. (2), as
well as to avoid unnecessary therapy, it still appears that a more
effective treatment strategy would be to (a) treat all of those with
positive antigen results and withhold therapy from as many as
clinically possible of the rest pending culture results (since neither
antigen assays nor culture can claim 100% sensitivity, the diagnosis
of group A streptococcal pharyngitis should include both clinical and
epidemiologic findings [3]), (b) perform cultures for
all patients with negative streptococcal antigen results, and (c) treat
the antigen-negative, culture-positive patients as currently
recommended (3).
(ii) The authors reported that 11 of the 15 false-negative antigen test
results came from patients whose cultures contained only rare to few
colonies of group A streptococci (2). The implication may be
that those patients with small numbers of streptococcal colonies from
culture are only colonized, not infected. This interpretation would be
in direct conflict with the conclusion of an excellent study by Gerber
et al. (1) that found that the differentiation of patients
with streptococcal infections from those who are only carriers of the
organism could not be made on the basis of the degree of positivity of
the culture alone.
| |
REFERENCES |
| 1.
|
Gerber, M. A.,
M. F. Randolph,
J. Chanatry,
L. L. Wright,
K. K. DeMeo, and L. R. Anderson.
1986.
Antigen detection test for streptococcal pharyngitis: evaluation of sensitivity with respect to true infections.
J. Pediatr.
108:654-658[Medline].
|
| 2.
|
Needham, C. A.,
K. A. McPherson, and K. H. Webb.
1998.
Streptococcal pharyngitis: impact of a high-sensitivity antigen test on physician outcome.
J. Clin. Microbiol.
36:3468-3473[Abstract/Free Full Text].
|
| 3.
|
Schwartz, B.,
S. M. Marcy,
W. R. Phillips,
M. A. Gerber, and S. F. Dowell.
1998.
Pharyngitis principles of judicious use of antimicrobial agents.
Pediatrics
101(Suppl.):171-174[Abstract/Free Full Text].
|
| | | | |
James A. Kellogg
Clinical Microbiology Laboratory
York Hospital
York, Pennsylvania
|
| |
AUTHORS' REPLY |
We appreciate Dr. Kellogg's careful reading of our paper. He raises a
very important concern with regard to long-term complications that
might be associated with use of the STREP A OIA test without culture confirmation.
After the introduction of point-of-care testing without reflexive
culture confirmation at the Lahey Clinic, we attempted to answer
questions about long-term patient outcome using the Lahey Clinic's
Decision Support System. Using ICD-9 codes for diagnoses and CPT codes
for testing, we identified 30,036 patients with a primary diagnosis of
pharyngitis managed during a 4-year period (data are summarized in
Table 1). The Lahey group practice saw about half of the patients
(15,399) in the 2 years preceding the introduction of the OIA test
(period 1). They saw the remainder of the patients (14,637) in the 2 years following the introduction of the OIA test (period 2).
During period 1, physicians ordered throat cultures for 65.6% of
patient encounters, using no tests in the other 34.4%. During period
2, physicians ordered the OIA test as the sole test in 50.8% of
patient encounters, a throat culture as the sole test in 14.3% of
patient encounters, the OIA test with culture confirmation in 1.3% of
patient encounters, and no test in the remaining 33.7%. This change in
diagnostic strategy was statistically significant (P < 0.001).
Using ICD-9 codes for suppurative and nonsuppurative complications of
pharyngitis and chart review, we found no significant difference
between the numbers of patients with complications during the two
periods. Analysis of period 1 identified 56 patients with peritonsillar
abscess, retropharyngeal abscess, or cervical lymphadenitis. Analysis
of period 2 identified 43 patients with a similar distribution of
suppurative complications. No patient was diagnosed as having acute
rheumatic fever during either period.
We concluded that providing a point-of-care test with characteristics
equivalent to the STREP A OIA test without culture confirmation improves patient management without sacrificing long-term quality of
care. We were able to achieve improved short-term patient outcome, increasing the number of patients treated appropriately during their
physician encounter. We increased the number of patients with group A
streptococci (GAS) who received a prescription for a full 10-day course
of therapy at the time of their visit. We decreased the number of
patients without GAS who received a prescription for an unnecessary
antibiotic. We also demonstrated no change in long-term outcome
associated with this system-wide change in diagnostic strategy.
| | | | |
Cynthia A. Needham
Kenneth A. McPherson
Ican Productions
Stowe, Vermont
|
| | | | |
Kenneth H. Webb
Biostar, Inc.
Boulder, Colorado
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Journal of Clinical Microbiology, June 1999, p. 2118-2119, Vol. 37, No. 6
0095-1137/99/$04.00+0
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