Standardization and Evaluation of the Clinical Usefulness
of Mycobacterial Skin Test Antigens
CDC, assisted by selected physicians and health departments
throughout the United States, recently completed a study to
determine
biologically equipotent doses for skin test antigens prepared from
several species of nontuberculous mycobacteria (NTM). This
standardization study was planned as a first step in evaluating the
clinical and epidemiologic usefulness of the NTM antigens. In the
past, these antigens were formulated on a protein-weight basis
equivalent to intermediate strength (5 TU) tuberculin-purified
protein
derivative (PPD) (0.1 ug/dose) and contained no stabilizer to
reduce
losses from adsorption to the container.
To standardize the individual NTM antigen, consenting patients
with compatible signs and symptoms and bacteriologically confirmed
NTM
disease received four skin tests of differing strengths of the
antigen
prepared from the homologous species of Mycobacterium and
stabilized
by Tween-80R. The skin tests were administered and measured by one
experienced nurse, and the amount of induration was measured at 48
hours. Dose-response curves for each antigen were used to estimate
the concentration bioequivalent to 5 TU of PPD-S (international
standard tuberculin), i.e., the dose expected to produce a mean
reaction of 16.0 mm induration, which is the mean reaction to 5 TU
of
PPD-S observed among a series of tuberculosis cases. From these
data,
standardized doses of PPD-B (M. avium complex), PPD-Y (M.
kansasii),
PPD-G (M. scrofulaceum), and PPD-platy (M. marinum) have now been
prepared (Table 1).
Reported by J Shinnick, Bucks County Health Dept, Pennsylvania; LB
Reichman, MD, UMDNJ, New Jersey Medical School, Newark; E Wolinsky,
MD, Cleveland Metropolitan General Hospital, Cleveland, Ohio; P
Smith,
MD, SUNY Health Science Center at Brooklyn, R Dattwyler, MD, SUNY
Health Science Center at Stoneybrook, New York; J Landis, MD, Bay
State Medical Center, Springfield, Massachusetts; R Ratard, MD, New
Orleans, Louisiana; DP Schlueter, MD, Medical College of Wisconsin,
Milwaukee; RJ Wallace, Jr, MD, University of Texas Health Science
Center, Tyler, C Ahn, MD, Dallas; CR Horsburgh, Jr, MD, University
of
Colorado Health Science Center, Denver; M Marks, MD, University of
Oklahoma Health Science Center, Oklahoma City; R Hayes, MD, New
Mexico
Health Svcs Div, Santa Fe; Respiratory Disease Br, Div of Bacterial
Diseases, Center for Infectious Diseases, Div of Tuberculosis
Control,
Center for Prevention Svcs, CDC.
Editorial Note
Editorial Note: A battery of standardized skin test antigens,
including tuberculin and those prepared from NTM, has several
potential uses: distinguishing mycobacterial from nonmycobacterial
diseases; distinguishing M. tuberculosis from NTM infections and
diseases; and distinguishing among specific NTM infections. This
diagnostic potential could not be adequately assessed using the
nonstandardized and nonstabilized preparations.
CDC is now beginning two studies to determine the clinical
usefulness of the standardized NTM antigens. Adults with suspected
mycobacterial pulmonary disease and children with chronic cervical
lymphadenitis will be offered a battery of four standardized skin
test
antigens: PPD-B, PPD-Y, PPD-G, and PPD-tuberculin. The test
results
will be compared to the mycobacterial species subsequently isolated
from the patients to determine the operational characteristics of
these tests, e.g., sensitivity, specificity, and predictive value.
Physicians interested in participating in these studies should
contact
CDC's Tuberculosis Clinical Research Branch at (404) 329-2530.
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