IJPHCS Open Access: e-Journal
International Journal of Public Health and Clinical Sciences e-ISSN : 2289-7577.Vol. 2:No. 2 March/April 2015
D-DIMER ASSAY IN DIAGNOSIS OF DEEP VEIN THROMBOSIS: LOCAL EXPERIENCE IN A GOVERNMENT HOSPITAL 2012-2013 Siti Hajar D 1, Jacky Tein Fuwen 1, Suraini M S 2, Hasyma A H 2* 1
Medical School, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia. Imaging Department, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia.
2
*Corresponding author: Hasyma Abu Hassan, Imaging Department, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia. Email:
[email protected]
ABSTRACT Background: Deep vein thrombosis (DVT) is a common complication of hospitalization. About 1 in 1000 adults is diagnosed with DVT. Although, conventional venography is the gold standard in diagnosing DVT, Doppler ultrasound has been globally accepted as the modality of choice given its accessibility and less invasive nature. The objective of the study is to determine the correlation between D-dimer level and lower limb doppler ultrasound (DUS) in suspected DVT patients. Materials and Methods: A cross-sectional study using retrospective data from January 2012 to July 2013 at Serdang Hospital. One hundred patients with suspected DVT who had undergone DUS were selected as samples. They were selected by convenience sampling method, and their data were recorded in the pro-forma. The data obtained was analyzed using statistical package for social sciences version 18.0 (SPSS 18.0) to determine any relationship. Result: Sensitivity of D-dimer test in Hospital Serdang was 95.8% while the specificity was 17%. However, when the subjects were grouped according to the risk factors, following Well’s criteria, the sensitivity and negative predictive value (NPV) of D-dimer test in low risk group were found to be 100%. There was also concordance between D-dimer test and DUS among the high risk group patients. The sensitivity and positive predictive value (PPV) of Ddimer test in high risk group patients were found to be 100%. Conclusion: This study reveals that D-dimer test has a very low specificity but can be used as a rule out test of DVT in low risk patients thus obviates the need for further imaging test. Meanwhile the high risk group patients can directly proceed with DUS for confirmation without performing D-dimer test, thus saving time in patient’s management as well as being cost effective. Keywords: d-dimer, deep vein thrombosis, doppler ultrasound
Siti Hajar D , Jacky Tein Fuwen , Suraini M S , Hasyma A H
13
IJPHCS
International Journal of Public Health and Clinical Sciences e-ISSN : 2289-7577.Vol. 2:No. 2 March/April 2015
Open Access: e-Journal
1.0 Introduction Deep vein thrombosis (DVT) is a common complication of hospitalization. About 1 in 1000 adults is diagnosed with DVT (Severinsen MT, 2010). In general surgical patients, Asian studies revealed an incidence ranging from 2.2% to 15.3% (Tun M and et al, 2001). The most common complication of DVT is pulmonary embolism. In untreated DVT, about 30% of the patient may develop pulmonary embolism (Anderson FA Jr, 2003) and the incidence is about 10 to 30 per 100 000 population in United State every year (White, 2003), (Anderson FA Jr, 2003) and (Kearon, 2003). Another frequent complication is post thrombotic syndrome which is characterized by chronic, persistent pain, swelling and ulceration in the affected limb (Tovey C, 2003). In view of its complication, prompt diagnosis and management of the deep vein thrombosis are important. Out of the diagnostic procedures for DVT, venography is the only invasive test of proven value (Line, 2001). However, due to its invasive nature, venography is not widely favoured as the modality of choice. Doppler ultrasonography (DUS) is considered to be the best non-invasive diagnostic method and has been evaluated against venography in many studies, showing an average sensitivity and specificity of 97% for proximal deep vein thrombosis (Scarvelis, 2006). D-dimer is a fibrin degradation product (FDP) which is a small protein fragment by-product of a fibrinolysis process. In normal physiological condition, the D-dimer is absent in the blood except when the coagulation system is activated (Adam SS, 2008). The principle of the Ddimer test is to detect the D-dimer concentration in the blood by using the monoclonal antibodies which will bind to the epitope of d-dimer. Our study was to look at the value of D-dimer test in correlation with Doppler Ultrasound in the diagnosis of deep vein thrombosis.
2.0 Materials and Methods This was a retrospective cross-sectional study using data from January 2012 to July 2013 at Serdang Hospital. Patients with suspected DVT who had undergone DUS were selected by a convenient sampling method. Those without the d-dimer results were excluded from the study. Their data was recorded in the pro-forma (Figure 1). The patients were later divided into low, moderate and high risk groups based on their clinical probability of deep vein thrombosis using Well’s Pretest probability (Figure 2). Statistical Package for Social Science (SPSS) version 21 was used to analyse the selected data. The sensitivity, specificity, positivepredictive value and negative predictive value of d-dimer test were calculated based on the demonstration of the DVT on Doppler ultrasound.
Siti Hajar D , Jacky Tein Fuwen , Suraini M S , Hasyma A H
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IJPHCS Open Access: e-Journal
International Journal of Public Health and Clinical Sciences e-ISSN : 2289-7577.Vol. 2:No. 2 March/April 2015
Figure 1: Pro forma
Figure 2: Well’s Pretest Probability for DVT Siti Hajar D , Jacky Tein Fuwen , Suraini M S , Hasyma A H
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IJPHCS
International Journal of Public Health and Clinical Sciences e-ISSN : 2289-7577.Vol. 2:No. 2 March/April 2015
Open Access: e-Journal
3.0 Result 3.1 Socio-demographic pattern of respondents 100 subjects were recruited for the study; 54 of which were male and the remaining 46 were female. The respondents were then divided into 2 age groups; 20-50 and 50-80 years old, with a larger percentage of those above 50 years old (62%). Ethnic distribution was also determined with Malays being the largest representative group (59%) as opposed to Chinese (22%) and Indian (19%). The socio-demographic distribution is summarised in Table 1. Table 1: Socio-demographic distribution Variables
Frequency
Percentage
20-50
38
38
51-80
62
62
Male
54
54
Female
46
46
Malay
59
59
Chinese
22
22
Indian
19
19
Age
Gender
Race
3.2 D-dimer level association with the demographic factors D-dimer assay is considered positive if the level is > 0.5mg/ml. Using Fisher’s exact test, no significant association was found between the demographic factors and the d-dimer level with p value >0.05. 3.3 D-dimer level with Well’s score The respondents were divided into 3 groups based on their Well’s score; low risk (Well’s score 0), moderate risk (Well’s score 1-2) and high risk (Well’s score 3). No significant Siti Hajar D , Jacky Tein Fuwen , Suraini M S , Hasyma A H
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IJPHCS
International Journal of Public Health and Clinical Sciences e-ISSN : 2289-7577.Vol. 2:No. 2 March/April 2015
Open Access: e-Journal
association was also found with different groups of Well’s score as shown in Table 2 (p value=0.761). Table 2: Association between D-dimer level with different Well’s score group. D-dimer Result
Well’s score
Total
Positive
Negative
0 (low risk)
32
5
37
1-2
51
9
60
3
0
3
86
14
100
P value
0.761
(moderate risk) 3 (high risk) Total
* using chi-squared test 3.4 D-dimer assay sensitivity and specificity against Doppler Ultrasound Table 3: D-dimer results against visualisation of DVT on Doppler Ultrasound DVT Positve
Negative
Total
D-dimer
Positive
23
63
86
result
Negative
1
13
14
24
86
100
Total
The specificity and sensitivity of D-dimer assay were calculated at 17.1% and 95.8% respectively with high false positive results. 3.4 The concordance between the D-dimer and doppler ultrasound among the low, moderate and high risk groups Despite further categorising the respondents into different risk groups based on Well’s score, no significant association was found between the D-dimer assay and DUS with high false Siti Hajar D , Jacky Tein Fuwen , Suraini M S , Hasyma A H
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IJPHCS
International Journal of Public Health and Clinical Sciences e-ISSN : 2289-7577.Vol. 2:No. 2 March/April 2015
Open Access: e-Journal
positive results in both the low and moderate risk groups. There is however, 100% concordance in the high risk group. Looking at different risk groups, the negative predictive value for the D-dimer assay in the low risk group is 100%.
Table 4: The concordance between the D-dimer and doppler ultrasound among the low, moderate and high risk groups Risk Group
D-dimer result
Doppler Ultrasound result Positive
Negative
P value
Low Risk group
Positive
1
31
(Well’s score : 0)
Negative
0
5
Moderate Risk
Positive
19
32
Group
Negative
1
8
High Risk group
Positive
3
0
(Well’s score : 3)
Negative
0
0