Express definition of D-dimer - an adequate method of exclusion of venous thromboembolism.

According to several meta-analysis of clinical studies, negative results of laboratory studies on D-dimer (DD) in combination with low clinical probability of venous thromboembolism (VT) allows sufficiently accurate to exclude the diagnosis of deep-vein thrombosis (DVT) and pulmonary embolism (LE). In this case, the clinical probability was assessed by valid rules (the indices) before the imaging studies (so-called pretest probability), and the definition of DD was performed in clinical laboratories using special equipment (e.g., by enzyme immunoassay ELISA) in recent years, rapid tests (ET) for determining the content of DD in a few minutes in the place of inspection of the patient (point of care). Such tests may be useful to doctors of primary ambulatory care, and intensive care units, to quick exclude the diagnosis Tues As a result. There is no need to use the central lab and waiting for the results of the analysis, and, most importantly, to conduct additional expensive imaging studies to diagnose Tues Dr. GJGeersing et al. (University of Utrecht, The Netherlands) conducted a systematic review and meta-analysis of studies evaluating the diagnostic accuracy of the ET definition of DD.

Methods and progress in the study.
Search of studies published in English before 1 September 2008, was conducted in Medline and Embase. Criteria for inclusion of studies in the meta-analysis: 1) participant - adult outpatients with suspected DVT and / or LE and 2) the use of ET in the doctor's office or emergency room at the time of patient examination, and 3) the application of verification methods of DVT (compression ultrasonography, venography, impedance plethysmography) or clinical observation for at least three months after his expulsion, and 4) the application of verification method's Edelstein (computed tomography, angiography, ventilation-perfusion scan) or long-term clinical follow-up to its deletion, and 5) calculated the sensitivity, specificity, predictive value negative and positive results and the incidence of DVT and LE.

Researchers included two qualitative and two quantitative determination of ET DD.
Test SimpliRED D-dimer - a semi quantitative test, using samples of capillary or venous blood is mixed with a drop of reagent. A positive result indicates the appearance of visible agglutination within 2 minutes, which indicates the DD of more than 200 micrograms per liter.

Test Clearview Simplify D-dimer - a qualitative test. It requires 35 ml of capillary or venous blood, and two drops of reagent. A positive test occurs when the level of DD for more than 80 ng / ml, as evidenced by the appearance of pink and purple stripes in the test area within 10 minutes.
Cardiac D-dimer - a quantitative test, which requires 150 ml of venous blood, the test strip and a portable device (Cobas h 232; Roche Diagnostics). Results are displayed in the range from 0,1 to 4,0 mg / ml. Threshold of a positive result is 0.5 mg / ml. Duration analysis - up to 15 minutes.
Triage D-dimer - a quantitative test that uses 250 ml of venous blood mixed with EDTA, and portable device (Triage Meter Plus; Biosite). Quantitative measurement is in the range of 0,1-5 mg / ml. The threshold for a positive result - 0.35 micrograms / ml. Duration of analysis for 10-15 minutes.

Based on pooled data of selected research, the scientists calculated the sensitivity, specificity, positive predictive value and negative results. The latter value, as the most important for accurate diagnosis of exclusion BT was identified in three risk categories: low (the frequency of VT -
5%), moderate (the frequency of VT - 20%) and high (frequency of VT - 50%). According to published data, the frequency of events Tues ≤ 2% after the negative ET on DD (post-test probability) was taken as the allowable (safe).

Selected 23 studies that have included 13,959 patients with suspected Tues In the 12 studies used SimpliRED (n = 6796), seven papers - Clearview simplified (n = 5730), 4 - Cardiac D-dimer (n = 925), 2 - Triage D-dimer (n = 508). The average age of participants ranged from 38 to 65 years, the proportion of men - from 30% to 55%, the prevalence of VT - from 4% to 51%. In studies that used SimpliRED Tue's frequency was 18,7%, Clearview simplified - 8, 2%, Cardiac D-dimer - 33, 9% and the Triage D-dimer - 13, 2%.

When combining these studies, the sensitivity of ET determination for the diagnosis of DD Tues was 0.88 (95% CI 0,83-0,92), specificity - 0,70 (0,62-0,77). When assessing the sensitivity of the individual methods SimpliRED reached 0,85 (0,78 -0,90), Clearview simplified - 0,87 (0,81-0,91), Cardiac D-dimer - 0,96 (0,91-0, 98) and the Triage D-dimer - 0,93 (0,88-0,97). The specificity of the methods was 0.74 (0,69-0,78), 0.62 (0,54-0,69), 0.57 (0,52-0,62) and 0.48 (0,33 -0.62).

Predictive value of the negative results (ie excluding the diagnosis of friction at the negative ET) for all tests was good only in populations at low risk of disease. Thus, when a negative result SimpliRED, Clearview simplified, Cardiac D-dimer and Triage D-dimer post-test probability Tues was 1, 1% 1, 1% 0, 4% and 0, 9% respectively. Only when using the Cardiac D-dimer can reliably exclude the diagnosis of watts for patients at moderate risk (post-test probability - 1.7%).

In ambulatory patients with clinical suspicion of the use of ET Tues determine DD provides additional information useful for selecting further management of the patient, especially at low risk Tues calculated according to the clinical index. In this high-quality ERs showed less sensitivity (ie, greater number of false-negative results) but higher specificity (ie fewer false positives) than the quantitative tests Thus, the quantitative tests are more appropriate to exclude the diagnosis Tues, Particularly informative method looks Cardiac D-dimer, with which you can reliably exclude a diagnosis Tues patients of low and moderate-risk (although the number of studies using this method was small, and they did not include patients with suspected LE).

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