title: Light reflection rheography: a simple noninvasive screening test for deep vein thrombosis.
abstract: OBJECTIVE
  The clinical diagnosis of deep vein thrombosis (DVT) is unreliable. Contrast phlebography (CP) continues to be the gold standard, but it is invasive. Although duplex ultrasonography is an accurate, noninvasive alternative, it is expensive, technically demanding, and time-consuming. We postulated that light reflection rheography (LRR), a noninvasive method of assessing the quantity and rate of venous emptying, might be a reliable and inexpensive bedside approach to screening patients with clinically suspected DVT.
  
  
  METHODS
  With LRR, infrared light is beamed onto the skin, and the amount of backscattered rays are detected, which indirectly measures the amount of blood present in a volume of the epidermis beneath the LRR probe. Applied to the calf muscle pump, LRR can provide a noninvasive method of assessing blood volume changes in the sample area of skin, in response to venous hemodynamic changes in the lower limb.
  
  
  RESULTS
  Sixty-nine limbs in 61 patients undergoing CP for clinically suspected DVT over a period of 12 months also underwent LRR, either just before or within 24 hours of undergoing phlebography. The criteria for diagnosing DVT on CP were presence of filling defect or nonfilling of a venous segment. The result of LRR was considered positive for DVT if the rate of venous emptying was 0.35 or less. With these criteria a sensitivity of 96.4% and specificity of 82.9 were obtained. This resulted in a positive predictive value of 79% and a negative predictive value of 97.1%.
  
  
  CONCLUSIONS
  LRR is a simple, inexpensive, and noninvasive bedside test that takes 10 minutes to perform. It is highly sensitive with a high negative predictive value, detecting most cases of DVT, reliably ruling out DVT, and eliminating the need for more time-consuming and costly studies. Therefore it seems to be an appropriate screening test in patients with clinically suspected DVT.
authors.affiliation: Department of Vascular Surgery, Guy's and Lewisham Hospital, London, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Arora
authors.forename: D J
authors.initials: DJ
authors.lastname: Lam
authors.forename: C
authors.initials: C
authors.lastname: Kennedy
authors.forename: G H
authors.initials: GH
authors.lastname: Meier
authors.forename: R J
authors.initials: RJ
authors.lastname: Gusberg
authors.forename: D
authors.initials: D
authors.lastname: Negus
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010690:Phlebography; D017156:Photoplethysmography / Q000379:methods; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013924:Thrombophlebitis / Q000175:diagnosis* / Q000000981:diagnostic imaging