No abstract

Reference ranges (RRs) in coagulation are applicable only to specific analyser and reagent combinations and frequently need to be re-established if any of these are changed. In no other sphere of clinical laboratory practice are RRs more affected by such a wide range of multiple demographic and pre-analytical variables. For most routine clinical laboratories therefore, the collection of multiple, separate RRs is not feasible so a representative group of healthy adults such as laboratory staff frequently constitute the reference population from which these limits are calculated. Early morning venous samples were collected into glass B-D Vacutainers (Ref: 367691) from 221 healthy laboratory personnel (F= 159; M = 62) aged 20–63 yrs for both gender. Age groups were equally represented. Samples were processed on a Sysmex CA-1500 analyser within 1 hour of collection. Appropriate NCCLS guidelines were followed throughout. Reagents employed were - Actin FSL (APTT); Innovin (PT); Dade-Behring reference, calibration and deficient plasmas (factor assays); Dade-Behring kit ref: OWWR15 (ATIII); Chromogenix kit ref: 82209863 (Protein C). Outliers were excluded, data examined for normal distribution from histograms and significance levels calculated from the Anderson - Darling test of normality. RRs for normally distributed parameters were calculated using means ± 2SDs. RRs for non-normally distributed parameters were calculated using the log natural transformation and the antilog of 2.5- and 97.5- percentiles. Italicised parameters shown below are non-normally distributed. Parameter Reference Range Anderson Darling P-Value P-value for normal distribution Mann Whitney U-test (M versus F) *=significant difference PT sec 10.0 – 11.8 <0.005 0.003* APTT sec 24.7 – 31.7 0.006 0.232 TCT sec 13.8 – 17.4 0.035 0.198 Fib g/L Clauss 1.6 – 4.2 0.190 t-test not significant Fib g/L Derived 2.1 – 4.9 0.200 t-test not significant II % 82 – 133 <0.005 0.019* V% 70 – 150 0.021 0.303 VII % 60 – 164 0.008 0.037* X% 75 – 147 0.539 t-test not significant VIII % 48 – 204 <0.005 0.520 IX % 65 – 142 <0.005 0.275 XI % 61 – 142 <0.005 0.394 XII % 59 – 133 0.088 t-test not significant Protein C % 75 – 160 0.036 0.024* ATIII % 86 – 128 0.329 t-test not significant Kruskal Wallis tests on our data indicate that all coagulation factors are positively associated with age except factors IX and XII. Significant differences (p=0.014) in factor VIIIc was found between those of blood group O and non group O. Significant correlation was found between declining APTTs and associated increasing factor VIIIc when measured in individual volunteers.

No abstract

No abstract

Introduction Along with clinical assessment, D-dimer (D-d) assays are routinely used to exclude DVT. It has been suggested that measurement of derived fibrinogen (DF) may be an effective reflection of endogenously-derived thrombin generation and that ratios between this and Clauss-derived fibrinogen (CF) may be useful in determining whether patients have experienced, or are vulnerable to thromboembolic events. Some studies indicate that a D-d/fibrinogen ratio is significantly higher among patients with confirmed DVT. The purpose of this study was to determine whether DF/CF ratios in individuals are a useful adjunct to D-d assays in the detection of DVT compared to D-d assay in isolation. Methods Venous samples were collected into glass B-D Vacutainers containing tri-sodium citrate (Becton-Dickinson, Plymouth, UKRef: 367691) from 162 out-patients presenting to the medical admissions unit with suspected DVT. Laboratory staff (N=100) served as the normal control group. D-dimer (MiniVidas, BioMerieux), DF and CF (Dade-Behring reagents in combination with a CA1500 coagulometer) were measured on all patients and normal control samples within two hours of collection. Results Following clinical assessment (Wells scoring), 85 patients were considered not to have had a DVT. Doppler scanning confirmed DVT in 38 of the remaining patients and 39 were shown to be negative. Two sample t-test analysis of the data showed significant differences between DF and CF levels in the normal group (n=100), patients who did not have a DVT (n=124) and those who did have a DVT (n=38), (p = &lt;0.05 in each group). There was a significant difference in the DF/CF ratios between the three groups (p = 0.014, one-way ANOVA). The mean DF/CF ratios in the normal control group, patient negative group and patient positive group were 1.16, 1.22 and 1.24 respectively. There was no overall correlation between D-d and DF (correlation co-efficient = 0.646), D-d and CF (correlation co-efficient = 0.581) nor between D-d and DF/CF. Of the DVT positive patients, 26 had a raised DF whereas only 12 had a raised CF. Conclusion Our data suggest that DF/CF ratios cannot be used as an adjunctive marker of DVT when used in combination with D-d values. DF/CF ratios are significantly higher in patients attending for clinical assessment irrespective of whether they are DVT positive or DVT negative. This may be because fibrinogen is an acute phase protein which increases with various pathological states and stressful events such as the experience of attending hospital for investigation and assessment. Further work is required to determine whether DF/CF ratios can be used adjunctively when the D-d cut off value is significantly higher than that used conventionally.