Læknablaðið - 15.06.2000, Page 31

FRÆÐIGREINAR / NYR DOKTOR / GREINAR
ERLENDUM TÍMARITUM
ment of superficial perfusion in arbitrary units with
an instrument used in current study, the laser
Doppler perfusion imager PIM 1.0 (LDPI). This
study uses in vitro experiments with simulated patch
tests to investigate various factors that may affect
LDPI readings of patch tests with the goal of provi-
ding LDPI set-up models for readings of patch tests
on humans. Based on LDPI and visual readings of
normal skin, irritant and allergic patch tests, an
instrument set-up is suggested for reading patch tests
when non-pigmented test substances are tested on
white skin. Other aims are to study if there may be
inter-individual differences in perfusion of identical
patch tests and some factors that may affect super-
ficial perfusion or its assessment, to compare assess-
ments of reactions made with the LDPI and visually,
and to study the effect of various patch-test tech-
niques on test results of five allergens.
Apart from readings of simulated tests, more than
40,000 readings were performed on 71 subjects.
Transparent patches and application devices made
possible assessment of patches during their applica-
tion. Measurements of perfusion over time made
possible charting and comparison of variable perfu-
sion profiles among subjects tested with identical
tests.
The application device and vehicles may affect
perfusion of patch tests while perfusion assessment
may be affected by skin pigmentation and move-
ments during readings.
There was generally good agreement between
LDPI and visual assessments of highest reactivity of
reactions except for two of the allergens, one of
which was neomycin sulfate where reactions deve-
loped that were not morphologically classifiable as
allergic reactions with the assessment scale used.
There were indications that some of those reactions
may be positive. Early phase of reactions was in some
cases detected earlier with the LDPI than visually,
and the LDPI tended to detect the highest reactivity
of reactions earlier with two allergens.
While a positive dose-response relationship was
generally found for most allergens, the relationship
between application times and response varied con-
siderably by allergens. Time of highest reactivity of
reactions was generally unaffected by dose or appli-
cation time except for a single allergen, regardless of
reading methods.
The LDPI allowed decreased dose of two aller-
gens without affecting sensitivity. Transparent foils
allowed reduced allergen dose for perfusion readings
without affecting test sensitivity of the test popula-
tions.
Reactivity at edges of negative corticosteroid
patch tests may indicate later elicitation of a positive
test.
There is evidence that a suggested set-up of the
LDPI for reading of tests when non-pigmented test
substances are used on white skin may be inappro-
priate with pigmented substances.
Fræðigreinar íslenskra
lækna í erlendum
tímaritum
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• Trausti Yaldimarsson, Toss G, Löfman O, Ström M.
Three years’ follow-up ofbone density in adult coeliac
disease: significance of secondary hyperparathyroid-
ism. Scand J Gastroenterol 2000; 35: 3274-80.
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