Reproducibility of color Doppler imaging.

Full Abstract

PURPOSE: The aims of this study were: (1) to determine the intra-subject and inter-observer variability of color Doppler imaging (CDI) measurements and readings of the retrobulbar blood vessels, (2) to compare the difference invariability of CDI parameters in non-glaucomatous controls versus glaucoma patients, and (3) to provide calculations of minimum sample sizes for future CDI studies. METHODS: Patients with normal tension glaucoma (n=28), primary open-angle glaucoma (n=19) and non-glaucomatous controls of comparable age (n=22) underwent CDI on two occasions 1 month apart. Variability in CDI parameters was quantified using (within-subject) coefficients of variation. Based on this variability, minimum sample sizes were calculated to guide the design of future studies comparing CDI between and within groups. RESULTS: In general, within-subject coefficients of variation for measurements 1 month apart were comparable to previously reported short-term variations. Variability was higher in glaucoma patients than in non-glaucomatous controls. The minimum sample size required for glaucomatous study populations is larger than for non-glaucomatous controls. Smaller patient groups are required to detect change using the peak systolic blood flow velocities than using end diastolic velocities. Studies using a cross-over design require smaller sample sizes than studies with a prepost or particularly parallel design. CONCLUSIONS: This study provides extensive information on long-term intra-subject variability of CDI measurements in non-glaucomatous controls as well as glaucoma patients. Moreover, sample size calculations are provided for studies involving glaucoma patients as well as non-glaucomatous individuals, using three different commonly used study designs.

Author information

Author/s: Stalmans, Ingeborg (I); Siesky, Brent (B); Zeyen, Thierry (T); Fieuws, Steffen (S); Harris, Alon (A);

Affiliation: Department of Ophthalmology, University Hospitals Leuven, Campus St Raphaël, Leuven, Belgium. ingeborg.stalmans(-atsign-)uzleuven.be

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv für klinische und experimentelle Ophthalmologie (Graefes Arch Clin Exp Ophthalmol), published in Germany. (Language: eng)

Reference: 2009-Nov; vol 247 (issue 11) : pp 1531-8

Dates: Created 2009/10/08; Completed 2009/11/04;

PMID: 19760224, status: MEDLINE (last retrieval date: 11/4/2009, IMS Date: )

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