Olesen, H.

Schiøtz, P.O.

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11. Epidemiology/Registry S111
427 Choice of spirometry values in epidemiological research
H. Olesen1, P.O. Schiøtz1. 1Aarhus University Hospital Skejby, Cystic Fibrosis
Center Skejby, Arhus, Denmark
Spirometry values are used in epidemiologic and registry CF research, and generally
considered valid parameters for standards of care, morbidity and prognosis.
However, pitfalls exist when collecting and interpreting such values, especially when
comparing treatment regimens, centers or countries.
Methods: We analysed spirometry values (FEV-1 and FEF25−75) from CF center
Skejby during a 3 year period. The data were obtained prospectively in the daily
clinical setting following the ERS/ATS recommendations for spirometry. Analyses
performed included coefﬁcient of variation, comparison of mean and max values,
and various calculations of slope.
Results: For FEV-1 56% of patients varied more than the normal CF inter-test
variation over a 12 month period. For FEF25−75 the number was as high as 86%.
For comparison of mean vs max values on a center level we found a visible, but
not signiﬁcant difference. For FEV-1 there was a 6% difference using the two
methods (p = 0.052) and for FEF25−75 a 12% difference (p = 0.067). 4 different
ways of calculating decline of lung function were performed. Though the results
varied slightly there was no signiﬁcant difference. Decline was steepest in patients
with FEV-1 of >100% or between 40 and 59%.
Conclusion: One single value of FEV-1 may be used a valid marker of that patient’s
lung function, whereas FEF25−75 varies too much. Comparing mean to max values
on a center basis may grant seemingly large differences. Consensus on method must
be reached. Calculation of slope can be done in various ways with little difference
in results.
428 Comparing the ‘best’ spirometry values of the year with values
obtained at the ‘last’ consultation in cystic ﬁbrosis patients in
Belgium using the CF Registry data
S.S. Wanyama1, M. Thomas1, H. Jansen1, on behalf of all members of the
BMR-RBM. 1Institute of Public Health, Epidemiology Department, Brussel,
Belgium
Objectives: To compare the best % of predicted FEV1 and FVC with values
obtained at the last consultation among CF patients.
Methods: The calculations of the % of predicted FEV1 and FVC were done
for patients 6 years and above excluding transplants. Means (±SD) and medians
(Interquartile range) were calculated for the overall population, by gender and age
groups. The Wang (6−17 years) and Hankinson (18 and above) prediction equations
were used.
Results: The overall means for the best % of predicted FEV1 and FVC of the year
were 80.9 % (±24.3) and 94.8 % (±19.7) respectively while the last values were
76.6 % (±25.2) and 90.9 % (±21.0). The mean best versus last % of predicted
FEV1 was 82.6 % (±24.6) and 78.3 % (±25.7) respectively in males, and 79.0
% (±23.7) and 74.7 % (±24.5) in females. The overall mean differences between
the best and the last FEV1 and FVC values were 4.3 % (±7.5) and 3.8 % (±7.3)
respectively, all p-values <0.0001.
Conclusions: The results show an overall signiﬁcant statistical difference between
the best and the last % of predicted FEV1 and FVC of about 4 %, even by gender and
across most age groups with the greatest difference in the age group 18−24 years.
The difference obtained was not within a clinically relevant margin of 5%. This
means values reported by the Belgian CF registry and other registries that use the
last values of the year are on average 4% lower than those used for benchmarking
by European Cystic Fibrosis Registry. These registries can still report these values
without fear of being seen as having worse patients compared to other registries
and thus maintain continuity of the data recording in their registries.
429 Trends in the incidence of acute kidney injury in UK cystic ﬁbrosis
patients
A. Prayle1, A. Knox2, A. Fogarty3, A. Watson4, A. Smyth1. 1University of
Nottingham, Academic Child Health, Nottingham, United Kingdom; 2University of
Nottingham, Respiratory Biomedical Research Unit, Nottingham, United Kingdom;
3University of Nottingham, Epidemiology and Public Health, Nottingham, United
Kingdom; 4Nottingham University Hospitals, Children’s Renal and Urology Unit,
Nottingham, United Kingdom
Acute kidney injury (AKI) is a recognised complication of treatment with aminogly-
cosides (AG). Recent reports have established the increased risk of AKI in patients
with CF. Once daily dosing of AG is associated with less nephrotoxicity, whereas
intravenous (IV) gentamicin (though not tobramycin) use is associated with AKI.
We studied the rates of AKI in two time periods through a national survey and the
UK PortCF database and conducted a national survey of prescribing practice, to
assess AG usage and its association with AKI.
From 1997–2004, 55 cases of AKI were reported. In a subgroup of 24 in whom AKI
was conﬁrmed by inspection of the case notes, 13 cases (54%) required dialysis.
An estimate of the total number of cases of AKI requiring dialysis in this period is
27.50 (3.44 cases/year). From 2006–2009, 3.75 cases/year of AKI requiring dialysis
were reported via PortCF.
We undertook a questionnaire survey of prescribing practice in UK CF centres in
2006. We found that 12 (35%) of centres had changed to od dosing, 1 (3%) had
changed from gentamicin to tobramycin, and 8 (23%) of centres were still using
gentamicin.
Our pragmatic survey using all available data suggests that the incidence of AKI
may not have changed in the period 2006−09 compared to 1997–2004. In 2009
the UK CF Trust recommended that IV gentamicin should not be used in CF. We
plan to re-survey UK CF centres to see if gentamicin use has changed since the
2006 survey and to record the incidence of cases of AKI through PortCF in order
to ascertain if the recommendation to avoid IV gentamicin is associated with fewer
cases of AKI in the future.
430 The disease burden associated with transmissible Pseudomonas
aeruginosa strains in adult CF
A. Ashish1, M. Shaw1, D. Nazreth1, H. Tan1, T. Jordan1, M. Ledson1,
M. Walshaw1. 1Liverpool Heart and Chest Hospital, Liverpool, United Kingdom
Although chronic infection with transmissible Pseudomonas aeruginosa (Psa)
strains confers a poor prognosis in CF patients, the disease burden this places
on such individuals has not been studied. To investigate this further, using logistic
regression, we matched (for age, sex, BMI, FEV1, and time since diagnosis) 47 adult
CF patients chronically infected with the commonest UK transmissible Psa strain
(the Liverpool Epidemic Strain, LES) with 47 infected with unique Psa strains
and compared the impact of the CF disease on their lives in terms of the use of
routine medication, use of home IV therapy, outpatient attendances, and episodes
of hospitalisation over a 5 year period.
Fisher’s exact test and Mann–Whitney’s U test were used to analyse the data.
Although there was no difference in routine medication use or home IV therapy,
those infected with LES had more hospital admissions (median 8 [IQ range 3−12]
v 2 [1−6]; p< 0.001), more inpatient days (median 90 [ IQ 33–144] v 20 [0−60];
p< 0.001), more outpatient attendances ( median 34 [IQ range 18−49] v 21 [10−34];
p = 0.002), required more home oral antibiotics (median 3 [IQ 2−4] v 2 [1−3];
p = 0.002), and were more likely to receive treatment for CF related diabetes and
undergo TIVAD insertion (both 19 v 9, p = 0.03), than those chronically infected
with unique Psa strains, respectively.
This study shows that patients chronically infected with epidemic Psa strains have a
high disease burden compared to other adult CF patients, and conﬁrms the need to
prevent cross-infection with these organisms whenever possible. We are conducting
a study to assess the impact of these strains on quality of life in the adult CF
population.


Choice of spirometry values in epidemiological research 

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Choice of spirometry values in epidemiological research

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