Modifications in the Rourke-Ernstene Sedimentation Rate Method
The Rourke-Ernstene method1 for determination of sedimentation rate measures the sinking velocity of erythrocytes during the period of most rapid fall. This method is considered to be more accurate than those that utilize a single one hour reading,2 such as the Wintrobe, Cutler, and Westergren methods. Other advantages of the method are the following: A small volume of blood (1.5 ml.) is required, the volume of packed red blood cells can be determined, and correction for anemia based upon the hematocrit reading can be calculated. The Rourke-Ernstene tube is preferred to the Wintrobe tube because it is longer and has a wider lumen. The greater length delays the “packing phase,” and the increased width makes the tube easier to clean and to fill.
In the original Rourke-Ernstene method heparin was used as an anticoagulant. For this the dry potassium and ammonium oxalate mixture of Heller and Paul3 has been substituted in the Cleveland Clinic, because the oxalated mixture is more economical, more dependable, and simpler to prepare. Various workers have shown that the results are comparable with those obtained with heparin.2,4
Rourke and Ernstene recommended recording the time-distance readings, constructing a curve from these readings, and calculating the fall of erythrocytes in millimeters per minute from the slope of the straight-line portion of the graph. Estimation of the sedimentation rate from graphs proved to be too time-consuming for clinical use. The modifications first made and for years used by our laboratory were (1) the determination of the time required for. . .