Test 1 analyser for determination of ESR. 2. Experimental evaluation and comparison with RBC aggregometry.

BACKGROUND: Test 1 is a recently introduced technique claiming to determine Erythrocyte Sedimentation Rate (ESR) in 20 s. In contrast to the original Westergren procedure this new technique uses undiluted blood and operates at 37 degrees C. It is hypothesized that Test 1 is in fact an erythrocyte aggregometer and does not measure any sedimentation. METHODS: Test 1 results were compared to those obtained with StaRRsed, an automated ESR analyser based on the Westergren technique, and the results of both were correlated to various indices of red blood cell (RBC) aggregation, obtained with an aggrego--meter (LORCA). Measurements were made on blood from 75 patients with various rheumatic disorders. Furthermore, blood that was experimentally manipulated in order to affect RBC aggregation, i.e. by changing the hematocrit, by diminishing plasma protein concentration, by inducing hyperaggregation or by RBC rigidification, was tested on all three instruments. RESULTS: Generally in patient blood, Test 1 results demonstrated a higher correlation with the various aggregation parameters than StaRRsed. Highest correlation (R = -0.8)) with both Test 1 and StaRRsed outcome were seen with I(20), a RBC aggregation parameter directly related to the backscatter intensity. All experimentally induced changes in RBC aggregation paralleled closely those obtained with Test 1 while StaRRsed results followed a different course. CONCLUSIONS: The results obtained in this study strongly support the hypothesis that Test 1 measures only the RBC aggregation process and does not cover any of the indices directly linked to the sedimentation process as determined by the Westergren method.

Test 1 analyser for determination of ESR. 1. Practical evaluation and comparison with the Westergren technique.

BACKGROUND: various modifications of the Erythrocyte Sedimentation Rate (ESR) determination have been suggested since the original Westergren procedure that has been adopted as the gold standard by the International Council for Standardization in Haematology (ICSH). Recently, an automated method, (Alifax Test 1), based on a technique completely different from Westergren, has been introduced. MATERIAL AND METHODS: In this comparative study, ESR of blood from 680 patients with various rheumatic diseases was determined on both Test 1 and the StaRRsed automated ESR analyser which performs measurements in accordance with ICSH specifications. Furthermore the robustness of the new technique was evaluated. RESULTS: Direct correlation of Test 1 and StaRRsed measurements confirmed the results of previous studies: an overall correlation coefficient of R = 0.90. However, further statistical analysis showed that, depending on the instrument that was used, in 78 samples (i.e. 11.5%) the results could lead to different treatment suggestions. Furthermore it appeared that several procedural factors could influence the final Test 1 outcome. CONCLUSIONS: Due to its sensitivity for procedural variations, Test 1 measurements should be carried out under strictly standardized conditions. Especially at the higher ESR levels the Test 1 technique is, however, not a reliable alternative for the ICSH approved 'Westergren' method.

Beta-trace protein is not superior to cystatin C for the estimation of GFR in patients receiving corticosteroids.

OBJECTIVES: Comparison of the effect of corticosteroid therapy on the diagnostic performance of cystatin C (Cys) and beta-trace protein (bTP), two endogenous markers of GFR. DESIGN AND METHODS: Out of a total of 193 pediatric inulin clearance studies, a random sample of 85 steroid-free studies served to establish GFR prediction equations (eGFR), which were used to compare the remaining 76 steroid-free and 32 steroid-positive studies (median prednisone dose 33.0 mg m(-2) day(-1)). RESULTS: We found a positive relationship between prednisone dose and eGFR(betaTP) (b=0.414, p=0.0002) and a negative relationship with eGFR(cys) (b=-0.208, p=0.0091). Only Cys independently predicted GFR below 90 mL min(-1) 1.73 m(-2), both in steroid-positives (b=6.260, p=0.010) and steroid-negatives (b=6.845, p=0.012). Glucocorticoid therapy did not affect the accuracy in estimating GFR within 30% of measured GFR for Cys, while accuracy was lower with bTP (65.6% vs. 81.6%, p=0.08). CONCLUSION: Glucocorticoids have less impact on the diagnostic accuracy of Cys than bTP.

Measurement of cystatin C in capillary blood samples in pediatric patients.

We assessed whether the GFR marker cystatin C can be measured reliably in capillary blood samples in children with renal disease. Cystatin C was measured in venous and capillary blood samples obtained simultaneously from 48 children, and GFR was estimated using the Filler equation. Estimated GFR based on capillary cystatin C concentrations was higher than the venous cystatin C based GFR. The limits of agreement between estimated GFR based on capillary and venous measurements exceeded +/-20% at the upper reference concentration, which hampers the clinical usefulness of capillary sampling.