Phyllis A. Bonham, PhD, MSN, RN, CWOCN, DPNAP, FAAN
,
College of Nursing, Medical University of South Carolina, Associate Professor and Director, Wound Care Education Program, Charleston, SC
Teresa Kelechi, PhD, AP, RN, CWCN
,
Medical Univ of South Carolina, College of Nursing, Associate Professor, Charleston, SC
Martina Mueller, PhD, RN
,
Medical University of South Carolina, Associate Professor, Statistician, Charleston, SC
Jacob Robison, MD
,
Medical University of South Carolina, Professor, Department Vascular Surgery, Charleston, SC
PURPOSE: Ankle brachial index (ABI) is recommended to detect LEAD, but in patients with diabetes, renal disease or arthritis, the ABI can be elevated (> 1.3) due to calcified ankle arteries and toe pressures (TP) are recommended.
1,2 Study aims were to determine the validity of TP by a nurse (RN) using a portable photophlethysmograph (PPG) compared to tests performed by a vascular technologist (RVT) using laboratory equipment and reliability of repeated RN tests. Hypotheses were: RVT- RN differences of 15 mmHg or less indicated portable tests were equivalent to laboratory tests, and if approximately 95% of differences in repeated RN measures fell within 2 standard deviations, portable PPG had acceptable repeatability.
METHODOLOGY: A within subjects, comparative design was used to collect data on 58 limbs from a convenience sample (N = 30) recruited from a vascular laboratory. Data were analyzed by the Bland-Altman method 3 in which bias (mean difference) and precision (limits of agreement) were compared to a priori criteria for clinically important limits (15 mmHg) to assess equivalence of RVT/RN measures and portable PPG repeatability. Kappa statistic calculation 4 was used to assess RVT/RN agreement to detect LEAD (< 50 mmHg5).
RESULTS: Precision for RVT- RN TP exceeded the cutoff criteria (15 mmHg), while precision for repeated RN PPG measures fell within clinically important limits. Kappa calculation (K = 0.76) revealed substantial agreement (90%) between RVT/RN measures to detect LEAD (< 50 mmHg) with high sensitivity (79%) and specificity (94.6%).
CONCLUSIONS: Although portable PPG TP are not a substitute for RVT tests, the portable test's high level of agreement with the RVT to detect LEAD and its high sensitivity and specificity make it suitable to use for patients at high risk or with wounds, when the ABI is > 1.3, to determine healing potential and the need for referrals to the vascular laboratory, surgeon, or adjunctive therapies.
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