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Appropriate Interpretation of Lung Function and Exercise Capacity in a Longitudinal Follow-up of Preterm Children

Jane Kirkby and colleagues raised some interesting points in relation to our article (1). They are especially concerned that the sample size is too small in relation to the conclusions, and that inappropriate reference data might have been used.

The first remark concerns the nonsignificant difference in lung function and exercise parameters between preterm subjects with and without bronchopulmonary dysplasia (BPD). While writing the article, we were aware of the risks of using small numbers for this subanalysis, which may be a reason why the difference in some lung function and exercise parameters did not reach statistical significance. We hope that these results based on small numbers will be a stimulus for researchers to investigate preterm subjects with and without BPD in larger series.

Based on the data we presented and the analysis we performed, concern about the inappropriateness of the statement that "mean lung function parameters were within normal range among survivors of preterm birth" is not fully justified. The variation in lung function among the preterm group was responsible for these differences and not the equated reference values. Therefore, we did mention—at the end of our discussion—how important control groups are when reference data are not available.

We support fully the last remark in which is stated that our study made an important contribution to existing knowledge. It underlined that new data were presented, and we agree that further investigations are necessary.

Elianne J. L. E. Vrijlandt, Jorrit Gerritsen, H. Marike Boezen, René G. Grevink and Eric J. Duiverman

University Medical Center Groningen, Groningen, The Netherlands

FOOTNOTES

Conflict of Interest Statement: E.J.L.E.V. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. J.G. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. H.M.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. R.G.G. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. E.J.D. has participated as a speaker in scientific meetings organized and sponsored by various pharmaceutical companies (GlaxoSmithKline, Merck, Sharp & Dohme [MSD]) and received $100,000 in 2003 from MSD and $100,000 in 2004 and 2005 from UCB on research grants for participating in clinical trials.

REFERENCES

1. Vrijlandt EJLE, Gerritsen J, Boezen HM, Grevink RG, Duiverman EJ. Lung function and exercise capacity in young adults born prematurely. Am J Respir Crit Care Med 2006;173:890–896.[Abstract/Free Full Text]

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