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The Journal of Clinical Endocrinology & Metabolism 87(10):4541– 4546
Copyright © 2002 by The Endocrine Society
doi: 10.1210/jc.2002-020287
Hypothalamic-Pituitary-Adrenal Axis Function after
Inhaled Corticosteroids: Unreliability of Urinary Free
Cortisol Estimation
RICHARD S. FINK, LISA N. PIERRE, PETER T. DALEY-YATES, DAVID H. RICHARDS,
ANTHONY GIBSON, AND JOHN W. HONOUR
Chemical Pathology Department, West Middlesex University Hospital/Quest Diagnostics, Inc., Isleworth, Middlesex, United
Kingdom TW7 6AF; Clinical Pharmacology, GlaxoSmithKline Research and Development, Greenford, Middlesex, United
Kingdom UB6 0HE; Respiratory Therapeutic Group, GlaxoSmithKline, Uxbridge, United Kingdom UB11 1BT; and
Department of Chemical Pathology, University College London Hospitals, London, United Kingdom W1T 4JF
Free cortisol in the urine (UFC) is frequently measured in
clinical research to assess whether inhaled corticosteroids
(ICS) cause suppression of the hypothalamic-pituitary-adrenal axis. Thirteen healthy male subjects received single inhaled doses (of molar equivalence) of fluticasone propionate
(FP), triamcinolone acetonide (TAA), budesonide (BUD), and
placebo in this single blind, randomized, cross-over study.
UFC output was measured using four commercial immunoassays in samples collected in 12-h aliquots over 24 h. The
cortisol production rate was assessed from the outputs of cortisol metabolites. UFC showed a 100% increase over placebo
levels in the Abbott TDX assay after the administration of
T
HE POTENTIAL FOR systemic effects on the hypothalamic-pituitary-adrenal (HPA) axis after exogenous
steroids, including intranasal or inhaled corticosteroids
(ICS), is assessed frequently in both the clinical setting and
research studies. Physicians concerned about adrenal suppression in asthmatic patients receiving ICS have recourse to
a number of diagnostic procedures. These include the measurement of plasma cortisol at 0800 h, integrated plasma
cortisol concentrations over 24 h, 17-hydroxycorticosteroids
(17-OHCS), the measurement of saliva or urinary free cortisol
(UFC), and the plasma cortisol response to ACTH (1–5).
Of these options urinary measurements are the most commonly used because of the noninvasive nature and convenience of sample collection. Although determination of UFC
concentrations using automated immunoassays may be convenient, some systems may be subject to interferences from
compounds produced by the metabolism of oral steroids or
ICS (6 –10). Theoretically, this cross-reactivity could result in
falsely elevated results, thereby masking endogenous cortisol suppression. A second drawback is the question of sensitivity, because commercially available immunoassays for
urine samples were originally introduced for the detection of
cortisol excess (Cushing’s syndrome) and not for the detection of adrenal suppression. Under normal circumstances
Abbreviations: BUD, Budesonide; CI, confidence interval; FP, fluticasone propionate; GC-MS, gas chromatography-mass spectrometry;
HPA, hypothalamic-pituitary-adrenal; ICS, inhaled corticosteroids; 17OHCS, 17-hydroxcorticosteroids; TAA, triamcinolone acetonide; TCM,
total cortisol metabolites; UFC, urinary free cortisol.
BUD. The other assays detected variable suppression (ranging from 29 – 61% suppression for FP, 30 – 62% suppression for
TAA, and 25% suppression to 100% stimulation for BUD). Suppression was more pronounced in the first 12 h after TAA and
in the second 12 h after FP. Similar suppression was found in
each 12-h period after BUD. UFC estimation based on immunoassays after ICS may be an unreliable surrogate marker of
adrenal suppression. Many of the published studies describing or comparing the safety of different ICS should be reevaluated, and some should be interpreted with caution. (J Clin
Endocrinol Metab 87: 4541– 4546, 2002)
serum cortisol-binding globulin is saturated and binds most
of the circulating cortisol. The fraction of free cortisol filtered
by the kidney and excreted in the urine is thus small, and
UFC concentrations are inherently low. A small degree of
suppression may therefore result in even lower UFC concentrations (⬍50 nmol/liter urine), at which point the
precision of many commercial immunoassays may be unacceptable [for diagnostic purposes a precision ⬍10% is recommended (10)].
Despite these considerations there is no published work in
which the effect of commonly used ICS on standard UFC
assays has been studied rigorously. Therefore, we have investigated the effects of single doses (near the highest
recommended doses) of three inhaled corticosteroids, budesonide (BUD), triamcinolone acetonide (TAA), and fluticasone propionate (FP), on the HPA axis as measured by four
different UFC assays that are used frequently in routine and
research practice.
In addition, a gas chromatography-mass spectrometric
(GC-MS) technique (11) was used as a reference method for
estimating adrenal activity as total cortisol metabolites
(TCM). TCM includes most cortisol metabolites, approximates to cortisol production rates closer than those achieved
through measurement of 17-OHCS. The concentration of
TCM in urine is relatively high and can therefore be measured accurately and precisely even in patients with adrenal
suppression (12, 13). A second advantage of TCM is that this
analysis is not subject to interference from ICS and their
metabolites.
The doses of ICS administered were clinically relevant and
4541
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J Clin Endocrinol Metab, October 2002, 87(10):4541– 4546
anticipated to achieve systemic exposure that was likely to
have a measurable effect on the HPA axis in healthy subjects.
For each ICS, a similar molar dose was administered. These
doses were therefore not therapeutically equivalent (relative
potency of FP/BUD/TAA, 1:0.5:0.25) (14).
Subjects and Methods
Thirteen healthy male subjects were enrolled in the study with an
average age of 24.6 yr (range, 20 –34 yr) and body mass index of 25
kg/m2. All subjects gave written informed consent. Each subject had a
physical examination and routine hematology, blood chemistry, urinalysis, and drug screen on entry into the study. Adverse events were
recorded throughout the study period. One subject withdrew from the
study due to personal reasons after TAA and BUD.
The study was approved by the research ethics committee of the
South-Eastern Sydney Area Health Service, Australia, and was conducted at the James Lance GSK Medicines Research Unit (Sydney,
Australia).
This was a single center, randomized, single blind, four-way crossover study with washout periods of 1 wk between treatments. Subjects
attended the unit on the evening before each treatment and remained in
the unit until the end of each treatment period. The baseline 24-h urine
collection commenced at approximately 0730 h. The urine was collected
in two 12-h aliquots. All urine collections were kept refrigerated between
voids. The subjects received single inhaled doses of BUD, TAA, FP, or
placebo at approximately 0730 h in random order under supervision. All
urine was then collected over the subsequent 24 h. Urine volumes were
calculated from the urine weight, and 10-ml aliquots were taken from
each 12-h collection, frozen immediately, and stored at ⫺70 C until
assayed.
All study drugs were administered according to recommendations
via metered dose inhaler (TAA with an integrated spacer). BUD (Pulmicort, AstraZeneca, Wilmington, DE) was administered as 8 inhalations delivering 200 ␮g ex-valve (172 ␮g ex-actuator)/actuation. TAA
(Azmacort, Aventis Pasteur, Lyon, France) was administered as 16 inhalations delivering 200 ␮g ex-valve (100 ␮g ex-actuator)/actuation. FP
(Flixotide, GlaxoSmithKline, Middlesex, UK) was administered as 7
inhalations delivering 250 ␮g ex-valve (220 ␮g ex-actuator)/actuation.
The ex-actuator doses delivered were 1376, 1600, and 1540 ␮g for BUD,
TAA, and FP, respectively. All doses are within the maximum recommended daily dose. These doses are approximately equivalent on a
molar basis (3.2–3.7 ␮mol).
Methods
UFC was determined by four immunoassay methods using protocols
recommended by the manufacturers. In each case cortisol was extracted
into dichloromethane, and extracts were dried before reconstitution in
buffer or zero standards before the assay. UFC was measured by RIA
(Corti-Cote, Product 06B-256440, ICN Biomedicals, Inc., Costa Mesa,
CA) and automated immunoassays (DPC Immulite, Product LKC05,
Diagnostic Products, Los Angeles CA; Abbott TDX, Abbott Laboratories,
Abbott Park, IL; Bayer ACS 180, Chiron Corp., Norwood, MA). Assay
sensitivities were 4.5, 5.5, 7, and 14 nmol/liter, respectively. Assay
performances were continuously checked with quality control of assayed urine control samples (Products AU 2353 and AU 2352, Randox
Laboratories Ltd., Ardmore, Crumlin, UK) at two levels (Table 1). The
majority of results from the study were between the quality control
levels tested. All samples from each subject were analyzed in one assay
batch to minimize subject variations. None of the commercial kits had
been tested for cross-reaction with the agents administered. (Conversion
from Systeme International units to conventional units is based on the
formula: 1 nmol/liter cortisol ⫽ 36.1 ng/dl cortisol.)
Urinary steroid analysis of free and conjugated steroids was also
performed by GC with flame ionization detector and GC-MS as previously described (10). Steroids were extracted from urine onto solid phase
cartridges and eluted with ethanol. After enzyme hydrolysis of the
conjugates, all steroids were recovered with a second solid phase extraction. Steroids were converted to methyloxime-trimethylsilyl ether
derivatives that were stable for analysis by GC. After identification in the
chromatogram, the excreted amounts of cortisol metabolites were
Fink et al. • Urinary Free Cortisol after Inhaled Corticosteroids
TABLE 1. Performances of UFC assays monitored at two levels
and lower limits of quantification
Assay
Abbott TDX
Bayer ACS
180
DPC Immulite
Corti-Cote
Interassay variation
QC1
QC2
15.5%
108 nmol/liter
17.0%
40 nmol/liter
20.8%
106 nmol/liter
25.4%
77 nmol/liter
12.6%
257 nmol/liter
9.0%
117 nmol/liter
11.8%
236 nmol/liter
13.6%
185 nmol/liter
summed to produce a TCM excretion rate. This method has been validated in the context of assessing adrenal activity in patients receiving ICS (11, 12). Individual metabolites can be detected to a level of 50
␮g/24 h.
Statistical analysis
Cortisol measurements for each 12-h urine aliquot were summed to
give the full 24-h measurement pre- and posttreatment. Results are
presented as the geometric mean with 95% confidence intervals (CI).
Treatment-related suppression of absolute urinary cortisol or cortisol
metabolite excretion relative to placebo was estimated for each ICS
according to assay with pairwise comparisons of ICS and placebo. The
data were analyzed using two linear models. Absolute UFC and TCM
measurements were log transformed and fitted to a linear model, including terms for subject, period, treatment, assay, and treatment by
assay interaction. Baseline data were included in the model as a covariate. No adjustments were made for multiple comparisons. All statistical
tests were two-sided alternatives with a 5% level of significance. It is
common practice to present 24-h UFC as a ratio of creatinine excretion.
As the subjects were supervised and resident within a clinical research
unit, a complete 24-h urine collection was achieved in this study. However, when this correction was made, no difference in the result was
detected for creatinine-corrected data. These data are therefore not
presented.
All statistical analyses were carried out using SAS package (version
6.12, SAS Institute, Inc., Cary, NC).
Results
There were no serious adverse events reported during this
study, and no subject withdrew due to adverse events.
24-h UFC output before ICS administration
In general, all four UFC assays gave similar UFC per 24 h
results at baseline, although the Immulite gave consistently
higher values than the Abbott TDX, Bayer ACS 180, and
Corti-Cote (Table 2). The measurements were all within the
reported normal ranges for UFC (50 –300 nmol/24 h) (1).
When comparing the two 12-h aliquots, UFC excretion was
greater in the samples collected during the day (0730 –1930
h) than those collected overnight. This was evident for all
four immunoassays and GC-MS (Table 2).
24-h UFC output after ICS administration
No subject had a value below 50 nmol/24 h after placebo
as measured by all four immunoassays (Fig. 1). A number
of subjects showed UFC values less than 50 nmol/24 h
with each ICS, but not with each immunoassay. For example, after treatment no subject showed a value below 50
nmol/24 h with the Immulite system. In contrast, posttreatment UFC fell below this value, although it was still
Fink et al. • Urinary Free Cortisol after Inhaled Corticosteroids
J Clin Endocrinol Metab, October 2002, 87(10):4541– 4546 4543
TABLE 2. Baseline UFC excretion rates over 12 h and integrated 24-h samples, measured using different immunoassays (geometric
mean and 95% CI)
Assay
Abbott TDX
Bayer ACS 180
DPC Immulite
Corti-Cote
GC-MS (TCM)
Baseline UFC excretion (nmol or ␮g for TCM)
Daytime 12 h (0730 –1930 h)
73.6 (61.4 – 88.2)
64.9 (56.7–74.2)
84.6 (72.6 –98.5)
68.6 (59.3–79.5)
8210 (7076 –9527)
Overnight 12 h (1930 – 0730 h)
42.5 (33.5–53.8)
29.5 (19.6 – 44.4)
49.4 (38.9 – 62.8)
33.5 (25.5– 44.0)
4432 (4018 – 4888)
24 h
119.1 (103.8 –136.6)
98.7 (83.9 –116.0)
137.6 (121.0 –156.5)
105.4 (93.9 –118.4)
12674 (11187–14359)
FIG. 1. Individual UFC outputs over 24 h after placebo, FP, BUD, and TAA (lower reference limit, 50 nmol/24 h).
measurable by the Abbott TDX, Bayer ACS, and Corti-Cote
methods. With regard to treatment type, subjects receiving
FP had UFC values below 50 nmol/24 h in one, six, and
two cases (Abbott TDX, Bayer ACS, and Corti-Cote, respectively). After TAA and BUD, this was observed in one,
eight, and one subjects and in one, three, and two subjects,
respectively (Fig. 1).
Apparent cortisol suppression assessed by UFC and total
cortisol metabolite
In addition to the absolute UFC output, the change in
24-h UFC after each ICS was compared with the placebo
values. UFC excretion reported after placebo showed no
differences from baseline for any of the immunoassays. In
keeping with the absolute UFC values, changes in UFC
varied depending on the assay method used (Table 3).
Most strikingly, after BUD, UFC excretion appeared to
increase by 100% compared with placebo in those samples
assayed by the Abbott TDX system. This was significantly
different from the results of the other three immunoassays
(P ⬍ 0.001). Furthermore, the anticipated suppression of
cortisol excretion after a high dose of BUD was clearly
observed with the other immunoassays and varied from
⫺25% to ⫺39%. These were significantly different from
placebo (P ⬍ 0.01). A significant reduction of UFC was
detected after both FP (P ⱕ 0.003) and TAA (P ⱕ 0.002) for
all assays used. However, there was considerable variation
in the degree of suppression observed, ranging from 29 –
61% after FP and from 30 – 62% after TAA depending on
the immunoassay (Fig. 2). These differences reached statistical significance in many cases despite the small number of subjects in this study (Fig. 2).
All three ICS caused significant suppression of TCM excretion (27%, 24%, and 34% compared with placebo for FP,
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J Clin Endocrinol Metab, October 2002, 87(10):4541– 4546
Fink et al. • Urinary Free Cortisol after Inhaled Corticosteroids
TABLE 3. Effect of inhaled corticosteroids on UFC (nmol/24 h) compared with placebo)
Assay
Abbott TDX
Bayer ACS180
DPC Immulite
Corti-Cote
GC-MS (TCM)
a
FP
BUD
TAA
Ratioa (95% CI)
% Change
Ratioa (95% CI)
% Change
Ratioa (95% CI)
% Change
0.70 (0.56 – 0.88)
0.39 (0.31– 0.49)
0.71 (0.56 – 0.89)
0.51 (0.41– 0.65)
0.73 (0.62– 0.85)
⫺30
⫺61
⫺29
⫺49
⫺27
2.01 (1.61–2.53)
0.63 (0.50 – 0.79)
0.75 (0.60 – 0.94)
0.61 (0.49 – 0.77)
0.76 (0.65– 0.89)
⫹100
⫺37
⫺25
⫺39
⫺24
0.62 (0.49 – 0.77)
0.38 (0.30 – 0.47)
0.70 (0.55– 0.87)
0.46 (0.37– 0.58)
0.66 (0.56 – 0.77)
⫺38
⫺62
⫺30
⫺54
⫺34
Geometric adjusted mean.
BUD, and TAA, respectively; P ⱕ 0.001; Table 3 and Fig. 2).
However, this was generally less than that found with the
immunologically based assays.
Influence of sample collection time (day and overnight) on
apparent cortisol suppression
In addition to the 24-h UFC data, cortisol excretion over the
12 h during the day (0730 –1930 h) and the 12 h overnight
(1930 – 0730 h) was investigated. The apparent significant
increase in cortisol excretion after BUD seen in the Abbott
TDX system was most prominent in the first 0 –12 h of collection. For the other three immunoassays, there was no
obvious difference or pattern in cortisol suppression detected
in the two 12-h aliquots. There was a tendency for greater
effect on TCM excretion in the overnight collection compared
with the first 12 h, although this was not statistically significant (Fig. 3 and Table 4).
The degree of cortisol reduction (UFC or TCM) after FP
was greater in the overnight collections compared with the
day collection with the Abbott TDX, Bayer ACS, and GC-MS
methods (Table 4). This was significant for the Bayer ACS 180
and GC-MS methods (Fig. 3). The overnight collection
tended to suggest greater suppression than the 24-h collection with the Abbott TDX, Bayer ACS, and GC-MS methods,
although this was only significant with the Bayer ACS.
After TAA, in contrast to FP, there was a tendency for less
effect on cortisol excretion in the overnight collection compared with the first 12-h collection (although this was not
statistically significant). This was particularly apparent with
the Abbott TDX and Immulite systems, although the latter
was associated with large variability (Fig. 2).
Discussion
The results of this study demonstrate that the assessment
of adrenal suppression by measuring UFC is more problematic than previously realized and is markedly influenced by
the assay methods used as well as the protocol for urine
collection.
One of the most striking observations reported here is the
dramatic interference seen with BUD and the Abbott TDX
system. With this assay, BUD appeared to cause an increase
in cortisol excretion of 100%. This result is likely to reflect
cross-reactivity of BUD metabolites with the anticortisol antibody used in the assay. The main BUD metabolites formed
in man are 6␤-hydroxybudesonide and 16␣-hydroxyprednisolone (15), one or both of which may be detected by the
assay. This potential problem of exogenous oral corticosteroid and/or cortisol metabolite interference has been recognized previously (7–10), and immunoassay kit manufactur-
ers recommend extraction procedures to reduce this
problem. Despite pretreatment with dichloromethane, the
Abbott assay in particular was subject to interference generated by BUD or its metabolites. Although others have recognized cross-reactions with immunoassays in patients receiving oral prednisolone (7, 8), it is not acceptable to adjust
the measured cortisol for the presumed cross reactivity (16).
This is the first report showing that a commonly used ICS can
perturb assays used in the routine clinical laboratory. The
marked interference seen with BUD was not apparent with
the other assays used, although it may have been present to
a lesser extent. Of the ICS tested, BUD is chemically the
closest to prednisolone. Reports in which the effects of BUD
on the HPA axis have been evaluated using the Abbott system should be reviewed with caution (17), although the importance of this in serum or plasma has not been evaluated
in the present study.
In addition to the interference seen with BUD and the Abbott
TDX, this study has clearly demonstrated that the extent of
cortisol suppression after ICS administration is influenced by
the analytical method. The same urine sample could yield up
to a 2-fold difference in observed HPA axis suppression when
comparing the immunoassays and up to a 5-fold difference
when compared using the reference GC-MS method. Thus,
depending on the assay used, entirely different conclusions
may be drawn on the potential for and magnitude of HPA
effects induced by these ICS. Importantly, this variability was
only seen in the presence of ICS. After placebo, no significant
difference was detected between the immunoassays. Lack of
specificity and poor precision at low concentrations are the
likely explanations for this difference. Further, although significant suppression was detected for BUD, FP, and TAA by TCM
measurement, the reductions observed were generally lower
than those seen with the immunoassays. These data may be
more representative of the actual HPA axis effects, as the aforementioned caveats are not applicable.
Comparison of daytime urine collections with overnight
collections demonstrates that the timing of urine collection
can significantly influence the cortisol suppression detected.
The pharmacology and metabolism of the drugs may explain
these findings. The interference after BUD in the Abbott TDX
system was most prominent in the first 12 h posttreatment
urine collection. This supports the conclusion that the apparent increase in UFC is due to metabolite cross-reactivity
and is consistent with the short half-life of BUD and its
metabolites (18).
TAA produced marked suppression in the first 12-h period, however, particularly when using the Abbott TDX or
Diagnostic Products Immulite, but no significant effect was
Fink et al. • Urinary Free Cortisol after Inhaled Corticosteroids
J Clin Endocrinol Metab, October 2002, 87(10):4541– 4546 4545
FIG. 3. Cortisol (or TCM) excretion rates after FP, BUD, and TAA
treatment measured in 0- to 12-h, 12- to 24-h, and 24-h urine collection periods. Values are the percent change with 95% CI.
FIG. 2. Effects of FP, BUD, and TAA on 24-h cortisol (or TCM) excretion rates assessed using different assays. Values are the percent
change with 95% CI.
seen in the overnight collection. This is also likely to reflect
the 2.5-h half-life of TAA (19), with approximately 97% of the
dose being eliminated over the first 12-h collection period.
Therefore, an overnight collection after a single morning
dose of TAA would be inappropriate when assessing the
HPA effects of this ICS. On the other hand, FP has a plasma
half-life of 10 h from the metered dose inhaler (20), and in
some assays demonstrated more suppression in the 12- to
24-h collection than in the 0- to 12-h collection. Despite these
considerations, 12-h overnight collections are frequently
used in clinical medicine and clinical research to assess cortisol production. In view of the number of available ICS and
their respective pharmacokinetic profiles, collection periods
should be chosen to obtain meaningful information in all
cases.
Our results have implications beyond patient management. Immunoassays are used extensively in clinical trials to
assess and compare the safety of ICS, and a huge body of
literature has evolved over the past 10 yr. When evaluating
these reports, the reader should consider whether potential
cross-reacting substances were effectively removed from the
urine, and which immunoassay was selected for the ICS
under study. For example, based on our data, estimated 56%
and 79% reductions in overnight UFC excretion would be
observed in a study in which TAA and FP are compared with
samples measured on the Bayer ACS. In contrast, a study
using 24-h collections and the same analytical platform
would demonstrate reductions of 62% and 61%. The reference assay of TCM indicated suppressions of 34% and 27%
for TAA and FP, respectively, in 24-h collections. When examining UFC values below the reference range (50 nmol/24
h used here and other researchers have used similar limits)
(21–23), discrepant results would also be observed. For example, the combination of FP and the Bayer ACS would
show UFC suppression in 6 of 12 subjects. BUD and the Bayer
ACS would show suppression in 3 of 13. However, with the
Corti-Cote system, these identical samples would show suppression in 2 of 12 and 2 of 13 cases, respectively. Clearly, the
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Fink et al. • Urinary Free Cortisol after Inhaled Corticosteroids
TABLE 4. Effect of inhaled corticosteroids on UFC in 12 h samples after ICS compared with placebo
Assay
Abbott TDX
Bayer ACS180
DPC Immulite
Corti-Cote
GC-MS (TCM)
FP
BUD
TAA
0 –12 h
12–24 h
0 –12 h
12–24 h
0 –12 h
12–24 h
⫺27 (⫺45 to ⫺3)
⫺59 (⫺69 to ⫺45)
⫺31 (⫺48 to ⫺8)
⫺53 (⫺65 to ⫺38)
⫺12 (⫺29 to 8)
⫺44 (⫺61 to ⫺19)
⫺79 (⫺85 to ⫺69)
⫺32 (⫺52 to ⫺2)
⫺46 (⫺62 to ⫺22)
⫺51 (⫺63 to ⫺36)
⫹137 (78 –214)
⫺34 (⫺50 to ⫺22)
⫺31 (⫺48 to ⫺9)
⫺44 (⫺58 to ⫺26)
⫺13 (⫺29 to 7)
⫹27 (⫺11 to 82)
⫺53 (⫺67 to ⫺33)
⫺21 (⫺44 to 13)
⫺32 (⫺52 to ⫺3)
⫺41 (⫺55 to ⫺24)
⫺48 (⫺61 to ⫺31)
⫺68 (⫺76 to ⫺57)
⫺41 (⫺56 to ⫺22)
⫺57 (⫺68 to ⫺43)
⫺27 (⫺41 to ⫺11)
⫺16 (⫺41 to 20)
⫺56 (⫺69 to ⫺37)
⫺4 (⫺33 to 38)
⫺44 (⫺61 to ⫺20)
⫺44 (⫺57 to ⫺27)
Data are percentage change from placebo (geometric adjusted mean, 95% CI).
selected assay significantly influences the outcome and conclusions in such studies. The findings of our study may go
some way to explain the discrepancies in exogenous steroid
(inhaled and intranasal) HPA axis effects described in the
literature, although unfortunately the details of assays and
sample treatment are often omitted in published papers on
this topic.
In summary, our study shows that UFC results in subjects
receiving ICS can be determined by variables within the
methodology. These variables exert such powerful effects
that suppression or, indeed, normal function can be diagnosed with equal facility in the same individual depending
on the assay and collection protocol used. This has critical
implications for patient management as well as for clinical
research, where conclusions about ICS safety may need to be
reevaluated because of issues raised in this study.
Acknowledgments
Richard Hodkinson, Nina Joseph, and Manesha Patel performed the
steroid assays.
Received February 22, 2002. Accepted July 19, 2002.
Address all correspondence and requests for reprints to: Dr. R. Fink,
West Middlesex University Hospital/Quest Diagnostics, Inc., Chemical
Pathology Department, Isleworth, Middlesex, United Kingdom TW7
6AF. E-mail: [email protected].
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