CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 3, May/June 2022 AFRICA 135 acute to chronic stages, the values of VE, EV4/V, RV and t½ increased, and the value of V decreased. This may represent adaptation of venous capacitance to the chronic status. As chronic disease predominated in the study population, this was expected to reflect the measurement results. The correlation between t½ values and skin discolouration or oedema in the affected leg was examined. Although t½ values did not correlate with the presence of oedema in the right extremity, it was negatively correlated with skin discolouration (r = –0.38, p < 0.001). In other words, as t½ got shorter in the right extremity, the skin discolouration increased, and it decreased as t½ got longer. In the left extremity, t½ was negatively correlated with both the presence of oedema and skin discolouration. In other words, the lower the t½ measurement, the more oedema and skin discolouration was observed in those individuals. In similar articles, t½ was also negatively correlated with oedema (r = –0.28, p < 0.05) and skin discolouration (r = –0.58, p < 0.001).5 These results indicate that CVD patients can be evaluated better by combining physical examination and SGP. Since there was no control group in this study, the normal legs of participants, which had no pathology, were considered the control to demonstrate the diagnostic power of SGP. Venous DUS was taken as the gold standard, and sensitivity and specificity values of SGP were calculated accordingly. Sample values are given as findings since there are currently no accepted SGP cut-off values. In fact, for VE measurements, a value of 81.00 had a sensitivity of 83.5% and a specificity of 78.8% in patients with right-sided pathology, and a value of 80.50 for patients with a left-sided pathology had a 76.5% sensitivity and 89.6% specificity. For V measurements, the value of 6.57 had 86.9% sensitivity and 82.3% specificity for patients with right-sided pathology, and for patients with left-sided pathology, 6.77 had a sensitivity of 82.2% and a specificity of 97.1%. For EV4/V measurements, a value of 0.57 had a sensitivity of 76.9% and a specificity of 82.3% in patients with right-sided pathology, and a value of 0.54 had an 87.6% sensitivity and 25.8% specificity in patients with left-sided pathology. For RV measurements, a value of 1.09 had a sensitivity of 78.2% and a specificity of 96.7% for patients with right-sided pathology, and for patients with left-sided pathology a value of 1.09 had a sensitivity of 75.2% and a specificity of 52.3%. For t½ measurements, 5.25 was found to have a 68.9% sensitivity and 99.7% specificity for patients with right-sided pathology, and for patients with left-sided pathology, 5.40 had a sensitivity of 78.3% and a specificity of 99.3%. In another study, SGP had an 84.6% sensitivity and 83.9% specificity in diagnosing DVT.20 In a study conducted in England, the sensitivity was 93% and specificity was 80%.16 In the study conducted by Langford et al. in 2009, the sensitivity was 93% and the specificity was 95%.10 As can be seen from the results, SGP can be used in both the diagnosis and follow up of CVD, including DVT and other venous insufficiencies. Although the results of this study cannot be adapted to the general population due to the limited number of patients and the absence of a control group, we consider SGP to be a good option for functional evaluation of patients with CVD. Replacement of the earlier strain gauges made of mercury with new indium gallium strain gauges gives SGP a more user-friendly design. This increased functionality makes SGP a cost-effective alternative to other plethysmographic devices used for similar purposes.21 Therefore SGP could be an alternative for clinicians who have limited access to a radiology service in remote settlements or require additional functional information obtained by clinical investigation and imaging techniques. Conclusion SGP was found to be an effective method in the diagnosis and follow up of CVD. In this study, we performed for the first time a detailed assessment of the influence of critical confounding factors and physiological variables on different plethysmographic measurements on the largest reported patient population in the literature. In addition, this study provides new reference values. As there are currently no accepted cut-off values, we suggest that ours can be used as new reference values for SGP measurements. We believe these results show increased usefulness of SGP in the functional assessment of patients with CVD and provide vital information, which was lacking on SGP. Conducting more comprehensive studies on this subject and determining the cut-off values for SGP measurements could provide earlier diagnosis and information on the degree of progression of CVD. References 1. Robertson L, Lee AJ, Evans CJ, Boghossian S, Allan PL, Ruckley CV, et al. Incidence of chronic venous disease in the Edinburgh Vein Study. J Vasc Surg Venous Lymphat Disord 2013; 1: 59–67. 2. Beebe-Dimmer JL, Pfeifer J, Engle JS, Schottenfeld D. The epidemiology of chronic venous insufficiency and varicose veins. Ann Epidemiol 2005; 15: 175–184. 3. Evans CJ, Fowkes FGR, Ruckley CV, Lee AJ. Prevalence of varicose veins and chronic venous insufficiency in men and women in the general population: Edinburgh Vein Study. J Epidemiol Community Health 1999; 53: 149–153. 4. 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Threedimensional CT venography of varicose veins of the lower extremity: image quality and comparison with Doppler sonography. Am J Roentgoenol 2008; 191: 1186–1191. 9. Spuentrup E, Buecker A, Stuber M, Günther RW. MR venography using True-FISP. Rofo 2001; 173: 686–690. 10. Langford NJ, Tonks K, Singh M. Out-patient detection of deep vein thrombosis using a combination of risk scoring and strain-gaugeplethysmography: a follow-up study. Acute Med 2009; 8: 127–130. 11. Rooke TW, Heser JL, Osmundson PJ. Exercise strain-gauge venous plethysmography: evaluation of a ‘new’ device for assessing lower limb
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