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DIAGNOSTIC ACCURACY OF SPLENIC ARTERY PULSATILITY INDEX IN PREDICTING FIBROSIS ASSOCIATED WITH CHRONIC HEPATITIS C.

Byline: Hidayat Ullah, Atiq Ur Rehman and Huma Aslam

ABSTRACT

Objective: To find the diagnostic accuracy of splenic artery pulsatility index in predicting fibrosis associated with chronic hepatitis C.

Study Design: Cross-sectional validation study.

Place and Duration of Study: Armed Forces Institute of Radiology and Imaging Rawalpindi, Departments of Medicine and Pathology, Pak Emirates Military Hospital Rawalpindi, from Sep 2014 to Feb 2015.

Material and Methods: Seventy-five patients with evidence of HCV infection as detected by positive anti HCV antibodies and HCV RNA for more than 6 months were recruited in this study using consecutive sampling. Ultrasound evaluation of liver and spleen was carried out after overnight fast along with doppler evaluation of splenic artery. Histopathological findings, of the subsequently done liver biopsy, were recorded as gold standard. Findings were recorded on the already prepared proforma. Statistical package for social sciences version 20 was used for the analysis of the data.

Results: The average age of the patients was 36.87 +- 8.16 years. Sensitivity, specificity, Positive predictive value, negative predictive value and diagnostic accuracy of increased splenic artery pulsatility index in assessing the severity of hepatic fibrosis were 80.8%, 91.8%, 84%, 90% and 88% respectively. ROC curve showed area under the curve to be 0.917 with p13 mm, hepatopetal velocity of 1.0 was considered to be abnormal. Liver biopsy was performed in department of medicine. Findings of doppler ultrasound and histopathology report were recorded on an already prepared proforma. All data was entered and analyzed by using SPSS version 20. For continuous variable (age) descriptive statistics like mean with standard deviation was calculated. For categorical variables (like gender and splenic artery pulsatility index) frequencies along with percentages were calculated. A 2x2 table was used to determine sensitivity, specificity, positive predictive value, negative predictive value and diagnostic efficacy.

Table-I: Descriptive statistics of age of the patients (n=75).

Statistics###Age(Years)

Mean###36.87

95% Confidence Interval for###Lower Bound###34.99

Mean###Upper Bound###38.74

Median###38.00

Std. Deviation###8.161

Minimum###21

Maximum###50

Interquartile Range###15

Table-II: Diagnostic accuracy of increased splenic artery pulsatility index by comparing it with histopathological changes.

Color Doppler and Spectral Doppler###Histopathology###Total

###Cirrhosis###Normal

Abnormal splenic artery pulsatility index(>1.0)###21(TP)###4(FP)###25(33.3%)

Normal splenic artery pulsatility index(a$?1.0)###5(FN)###45(TN)###50(66.7%)

Total###26(34.7%)###49(65.3%)###75

Sensitivity###=21/26###=80.8%

Specificity###=45/49###=91.8%

PPV###=21/25###=84%

NPV###=45/50###=90%

Accuracy###=(21+45)/75###=88%

RESULTS

A total of 75 patients with evidence of HCV infection were recruited in this study with average of the patients being 36.87 +- 8.16 years (table-I). There were 61.33% (n=46) males and 38.67% (n=29) females with male to female ratio of about 1.59. Splenic artery pulsatility index is presented in fig-1. Diagnostic accuracy of splenic artery pulsatility index in predicting fibrosis associated with chronic hepatitis C as shown by liver biopsy is presented in table-II. Abnormal SAPI (>1.0) was observed in 33.3% (n=25), out of which 21 cases were true positive (TP) on histopathology with positive predictive value (PPV) of 88%. Normal SAPI was observed in 66.7% (n=50), out of which 5 cases were found to be false negative (FN) on histopathology with negative predictive value (NPV) of 90%. Histo-pathologically, 34.7% (n=26) cases were found to be positive for fibrosis, out of which 5 cases had normal SAPI giving a sensitivity of 80.8%.

Liver biopsy showed no fibrosis in 65.3% (n=49), out of which 4 had abnormal SAPI giving a specificity of 91.8%. Accuracy of the color Doppler/spectral Doppler for detecting fibrosis associated with in chronic hepatitis C was found to be 88%. Receiver operating characteristic (ROC) curve for different cut off levels was plotted (fig-2). Sensitivity and specificity for cut off level value of SAPI >1.0 was found to be 80.8% (95% confidence interval of 60.6-93.4) and 91.8% (95% confidence interval of 80.4-97.7) respectively.

DISCUSSION

Ultrasonography being a readily available imaging modality is widely considered as a method of choice for the initial evaluation of hepatic parenchymal disease. The imaging findings as detected on ultrasonography in patients suspected to have chronic liver disease show a reasonably high concordance ranging between 74-88% in detecting hepatic cirrhosis13. HCV associated chronic liver disease spectrum not only entails parenchymal but also porto-splanchnic hemodynamic changes, both subsequently leading to the development of irrevocable end stage chronic liver disease10,14. In addition to hepatic parenchymal disease evaluation on grey scale imaging, the introduction of duplex doppler ultrasonography has proven to be a break-through in evaluation of splanchnic hemodynamic changes set in secondary to portal hypertension, a known insidious complication of chronic liver disease10,15, 16

Despite the availability of modern diagnostic facilities, the prevalence of advanced stage chronic liver disease among freshly diagnosed cases of hepatitis C is about 20%17. splenic artery impedance evaluation, although rarely employed in chronic liver disease evaluation, has proven to be an important indicator in assessing the severity of fibrosis in patients suffering from chronic liver disease18 In this study, the average age of the patients was 36.87 +- 8.16 years. Male to female ratio was 1.59. This corresponds well with Araujo who studied epidemiology of hepatitis B and C in Brazil and reported a male predominance and a mean age of approximately 40 years19. Portal vein and splenic artery, although appear to be lying at two ends of vascular spectrum, are intricately interconnected hemodynamically with the intra splenic arterial impedance showing an unexpected rise, correlating well with portal venous hypertension.

The exact pathophysiology behind this altered flow impedance in splenic artery is based on the presupposition that although the peak systolic velocity is based on cardiac systole, the end diastolic velocity is dependent on portal venous outflow. As portal hypertension sets in, there is resistance to venous outflow with subsequent development of venous congestion in spleen attributable to erythrocyte accumulation within the red pulp of spleen. Since vascular impedance depends on arterial resistance, venous compliance and venous congestion, an increase in venous congestion within the spleen leads to reduced diastolic velocities in the splenic artery and subsequently elevated resistance indices20.

Normal value for resistive index (RI=peak systolic velocity-end diastolic velocity/peak systolic velocity) is a$?0.63 while the normal value for pulsatility index (PI = Peak systolic velocity-End diastolic velocity/Mean velocity) is taken as a$?1.010,18, because of taking in to account mean velocity instead of peak systolic velocity, pulsatility index is preferred as compared to resistive index9,21. Bolognesi et al showed that portal pressure could be predicted by using a formula using the splenic PI and the portal vein flow22 splenic artery pulsatility index, thus, offers a non-invasive method of assessing the splenoportal haemodynamics and helps in predicting the status of the hepatic fibrosis and the resulting changes in the portal system due to chronic liver disease22. This study shows similar results confirming splenic artery pulsatility index to be a reliable predictor of hepatic fibrosis and portal hypertension.

Liver biopsy is considered to be the gold standard for evaluating and grading hepatic fibrosis. However, it is expensive and associated with significant risk of complications including patient discomfort, significant morbidity, and mortality23 Splenic artery pulsatility index offers a noninvasive tool for assessing chronic liver disease and associated hepatic fibrosis. This study shows that splenic artery PI is a good indicator of portal hypertension as a result of cirrhosis and the use of this simple technique can decrease the much invasive techniques like liver biopsy. This corresponds well with Liu et al who found splenic artery pulsatility index to be a precise and reproducible technique to assess the degree of hepatic fibrosis in chronic hepatitis C which could significantly reduce the number of staging liver biopsies8. Treatment given to patients of chronic liver disease depends on severity of liver damage.

End stage of liver disease does not have specific treatment except the management of complications24. On the other hand curative medical treatment in HCV infection can stop the progression of liver damage and is given to patients who have not already developed cirrhosis25. High sensitivity and specificity of SAPI in predicting hepatic fibrosis associated with chronic hepatitis C as shown by this study make Doppler examination of the splenic artery a useful alternative to liver biopsy for identifying liver fibrosis in non cirrhotic patients. The strength of our study is the comparison of Doppler findings in splenic artery with histopathologic changes as seen on liver biopsy. This made the objective assessment of pulsatility index as an indicator of hepatic fibrosis in chronic hepatitis C possible.

LIMITATION OF STUDY

Using a relatively small sample size is a limitation of the study. The study focuses on one parameter for predicting fibrosis associated with chronic hepatitis C while to avoid liver biopsy other parameters might also need to be taken in to account.

CONCLUSION

Splenic artery pulsatility index is a simple, non-invasive and reproducible technique for assessing hepatic fibrosis in patients with chronic hepatitis C and can reduce the number of staging liver biopsies.

RECOMMENDATION

Therefore, more studies with a large sample size and taking in to account other ultrasound parameters in local setup will be helpful in confirming the findings of this study and explore more relevant parameters.

CONFLICT OF INTEREST

This study has no conflict of interest to be declared by any author.

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Publication:Pakistan Armed Forces Medical Journal
Date:Dec 31, 2018
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