Reliability of laser Doppler flowmetry curve reading for measurement of toe and ankle pressures: intra- and inter-observer variation.
OBJECTIVE
To assess the intra- and inter-observer variation in laser Doppler flowmetry curve reading for measurement of toe and ankle pressures.


METHODS
A prospective single blinded diagnostic accuracy study was conducted on 200 patients with known or suspected peripheral arterial disease (PAD), with a total of 760 curve sets produced. The first curve reading for this study was performed by laboratory technologists blinded to clinical clues and previous readings at least 3 months after the primary data sampling. The pressure curves were later reassessed following another period of at least 3 months. Observer agreement in diagnostic classification according to TASC-II criteria was quantified using Cohen's kappa. Reliability was quantified using intra-class correlation coefficients, coefficients of variance, and Bland-Altman analysis.


RESULTS
The overall agreement in diagnostic classification (PAD/not PAD) was 173/200 (87%) for intra-observer (κ = .858) and 175/200 (88%) for inter-observer data (κ = .787). Reliability analysis confirmed excellent correlation for both intra- and inter-observer data (ICC all ≥.931). The coefficients of variance ranged from 2.27% to 6.44% for intra-observer and 2.39% to 8.42% for inter-observer data. Subgroup analysis showed lower observer-variation for reading of toe pressures in patients with diabetes and/or chronic kidney disease than patients not diagnosed with these conditions. Bland-Altman plots showed higher variation in toe pressure readings than ankle pressure readings.


CONCLUSIONS
This study shows substantial intra- and inter-observer agreement in diagnostic classification and reading of absolute pressures when using laboratory technologists as observers. The study emphasises that observer variation for curve reading is an important factor concerning the overall reproducibility of the method. Our data suggest diabetes and chronic kidney disease have an influence on toe pressure reproducibility.
Department of Clinical Physiology, Viborg Regional Hospital, Viborg, Denmark; Department of Health Science and Technology, Aalborg University, Aalborg, Denmark. Electronic address: ch@hst.aau.dk.
C
C
Høyer
Department of Clinical Physiology, Viborg Regional Hospital, Viborg, Denmark.
J P D
JP
Paludan
Department of Clinical Physiology, Viborg Regional Hospital, Viborg, Denmark.
S
S
Pavar
Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
J A
JA
Biurrun Manresa
Department of Nuclear Medicine, Aalborg University Hospital, Aalborg, Denmark; Department of Clinical Medicine, Aalborg University, Aalborg, Denmark.
L J
LJ
Petersen
D000368:Aged; D055109:Ankle Brachial Index / Q000379:methods*; D015897:Comorbidity; D003925:Diabetic Angiopathies / Q000453:epidemiology / Q000503:physiopathology; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008875:Middle Aged; D015588:Observer Variation; D058729:Peripheral Arterial Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D051436:Renal Insufficiency, Chronic / Q000453:epidemiology / Q000503:physiopathology; D015203:Reproducibility of Results
Ankle brachial index; Clinical laboratory techniques; Diagnostic test; Laser Doppler flowmetry; Peripheral arterial disease; Toe brachial index