Determination of the length of sedimentation reaction in blood using the TEST 1 system: comparison with the Sedimatic 100 method, turbidimetric fibrinogen levels, and the influence of M-proteins.
BACKGROUND
Determination of the length of sedimentation reaction in blood (LSRB) is frequently used in daily practice to assess disease intensity. Recently, a micro-sedimentation method was introduced (TEST 1) that uses EDTA anti-coagulated blood samples. The aim of this study was to characterize this method by comparing it to a conventional Westergren method (Sedimatic 100). Furthermore, correlation between fibrinogen and the LSRB and the influence of M-proteins on the LSRB was investigated.


METHODS
Unselected paired samples were used for comparison between the TEST 1 and Sedimatic 100 methods (n=733); fibrinogen was measured in EDTA samples (n=765) using a turbidimetric method. Furthermore, LSRB was measured in 29 EDTA samples in paired serum tubes from patients in whom an M-protein was detected.


RESULTS
TEST 1 showed excellent correlation with the Sedimatic 100 method (y=1.00x; n=733; r=0.92, 95% CI 0.90-0.93; p<0.0001), and had no significant bias (0.15 mm/h, 95% CI -0.48 to 0.75 mm/h). Furthermore, TEST 1 LSRB showed satisfactory correlation with the fibrinogen content (y=3.13+0.06x; n=765; r=0.78, 95% CI 0.75-0.80; p<0.0001). In samples containing M-proteins, satisfactory correlation between the M-protein content and TEST 1 LSRB was found (y=0.69+0.22x; n=29; r=0.71, 95% CI 0.45-0.85; p<0.0001), while excellent correlation was found when only M-proteins of the IgM type were taken into account (y=-0.95+0.23x; n=9; r=0.93, 95% CI 0.71-0.99; p<0.0002).


CONCLUSIONS
The results confirm previous reports that TEST 1 is a reliable method to measure the LSRB, and shows for the first time the quantitative relationship between TEST 1 LSRB and M-proteins, particularly those of the IgM type.
Ajubi
Nasser E
NE
Stichting KCL, Department of Clinical Chemistry, Leeuwarden, The Netherlands. n.e.ajubi@znb.nl
Bakker
Andries J
AJ
van den Berg
Gita A
GA
D001799:Blood Sedimentation; D005340:Fibrinogen / Q000032:analysis*; D006023:Glycoproteins / Q000097:blood*; D006403:Hematologic Tests / Q000379:methods*; D006801:Humans; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D013997:Time Factors
D006023:Glycoproteins; C023587:protein M (glycoprotein); D005340:Fibrinogen