Direct oral anticoagulant concentrations and adherence in stroke patients.

No therapeutic ranges linking drug concentrations of apixaban and rivaroxaban to clinical outcomes have been defined. We investigated whether direct oral anticoagulant (DOAC) concentrations among patients admitted to hospital with symptoms of stroke differed between those later verified to suffer an ischaemic cerebrovascular event (stroke or transient ischaemic attack) and those having other diagnoses (control group). Serum concentrations in 102 patients on DOAC for atrial fibrillation (84%) and thromboembolic disease (16%) were measured within 24 h of the acute event, employing ultra-high performance liquid chromatography with tandem mass spectrometry. We converted all concentrations to standardized trough levels. DOAC concentrations were lower in the 64 patients with verified ischaemic cerebrovascular event than in the 30 controls, 255 ± 155 versus 329 ± 144 nmol/L (p = 0.029), despite no statistically significant difference in self-reported adherence and daily dosages. Calculated concentrations were 5.4-596 nmol/L (median = 229 nmol/L) in the ischaemic stroke group and 41-602 nmol/L (median = 316 nmol/L) in controls. CHA2 DS2 -VASc score was significantly higher in the ischaemic stroke group than in controls (4.9 ± 1.6 versus 4.1 ± 1.7; p = 0.007). These results may suggest that patients with high cerebrovascular risk might benefit from higher DOAC levels than those with a lower risk.

Reference change values of FIB-4.

When comparing two analytical results for the same analyte, the clinicians may benefit from knowing the reference change values (RCVs) of the analyte. For Fibrosis-4 Index (FIB-4), a noninvasive test used for assessing the risk of liver fibrosis, no RCVs have been published for non-cirrhotic individuals. Therefore, we estimated RCVs for adults, using retrospectively collected data from outpatients with AST, ALT, and thrombocytes within the respective reference intervals. FIB-4 was calculated as (age × AST)/(thrombocytes × ALT0.5). From two FIB-4 values in each patient we calculated the RCVs parametrically and non-parametrically. For both methods, we estimated the limits of the central 90% of the distribution of the ratio between the second and the first measurement. We obtained data on 599 outpatients with two blood tests taken 3 - 972 (median 258) days apart. The RCVs were 0.72 - 1.40 and 0.72 - 1.43, respectively, using the parametric and non-parametric methods. The 5 and 95 percentiles were not statistically significantly associated with sex, age, level of analyte, or the time between the measurements. The within-subject biological variation of FIB-4 was estimated to be 13.9%. Conclusion: In 90% of the patients the ratio between the second and the first FIB-4 result was approximately 0.7 - 1.4.

Calprotectin and CRP as biomarkers of cardiovascular disease risk in patients with chronic kidney disease: a follow-up study at 5 and 10 years.

Chronic kidney disease (CKD) and low-grade inflammation are associated with increased risk of cardiovascular disease (CVD). Calprotectin, a protein mainly secreted by activated neutrophils during inflammatory conditions, has been linked to CVD risk in general populations. The aim of this study was to evaluate the association of calprotectin with CVD risk in CKD patients, relative to C-reactive protein (CRP). One hundred and fifty-three patients with moderate CKD were prospectively followed up at 5 and 10 years. We used Cox regression modelling with stepwise adjustments for other relevant covariates (age, sex, cystatin C, previous CVD, systolic blood pressure, HDL cholesterol and HbA1c) to assess the association of baseline calprotectin and CRP with the risk of fatal or non-fatal CVD events. Twenty-nine and 44 patients experienced a CVD event during median follow-up of 4.8 and 10.9 years, respectively. Higher calprotectin was associated with increased CVD risk at both time points, which remained statistically significant after multivariable adjustments, including adjustment for CRP. For CRP, the associations did not remain statistically significant after final multivariable adjustments. In conclusion, we have shown that in patients with CKD, calprotectin was independently associated with the risk of future CVD events, suggesting that calprotectin may provide prognostic information of CVD risk.

Inflammatory markers and risk of cardiovascular mortality in relation to diabetes status in the HUNT study.

Inflammatory markers have been associated with increased risk of cardiovascular mortality in general populations. We assessed whether these associations differ by diabetes status. From a population-based cohort study (n = 62,237) we included all participants with diabetes (n = 1753) and a control group without diabetes (n = 1818). Cox regression models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CI) for possible associations with cardiovascular mortality of 4 different inflammatory markers; C-reactive protein (CRP), calprotectin, neopterin and lactoferrin. During a median follow-up of 13.9 years, 728 (20.4%) died from cardiovascular disease (CVD). After adjustment for age, sex and diabetes, the associations of all inflammatory markers with risk of cardiovascular mortality were log-linear (all P ≤ 0.017 for trend) and did not differ according to diabetes status (all P ≥ 0.53 for interaction). After further adjustments for established risk factors, only CRP remained independently associated with cardiovascular mortality. HRs were 1.22 (1.12-1.32) per standard deviation higher loge CRP concentration and 1.91 (1.50-2.43) when comparing individuals in the top versus bottom quartile. The associations of CRP, calprotectin, lactoferrin and neopterin with cardiovascular mortality did not differ by diabetes, suggesting that any potential prognostic value of these markers is independent of diabetes status.

Using blood calprotectin as a measure of blood neutrophils.

Presently, bed-side or at home quantification of neutrophils in blood (b-neutrophils) is not practical, because cytometric methods are too expensive and technically demanding. We have explored whether calprotectin concentration in whole blood (b-calprotectin) might be a valid measure of b-neutrophils because this principle might be used in a simple and robust immunoassay device. We obtained heparin blood samples from 77 patients with possible neutropenia, most of them cancer patients treated with cytostatic drugs, and compared b-calprotectin with their b-neutrophils in a simultaneously taken EDTA-blood sample. The Spearman rank correlation coefficient between b-calprotectin and b-neutrophils was 0.986 (p < .0001). In a regression model of b-neutrophils as a function of age, gender, type of hematology instrument, total leukocyte count minus neutrophils, b-calprotectin, and plasma calprotectin (p-calprotectin), only b-calprotectin was a statistically significant predictor. B-neutrophils below 1 × 109/L was unlikely if b-calprotectin was above 50 mg/L. In conclusion, b-calprotectin, without adjusting for p-calprotectin, correlates closely with b-neutrophils and could be used to detect b-neutrophils below 1 × 109/L.

The individual systematic difference between CoaguChek and STA-SPA.

Using CoaguChek to measure PT-INR and comparing the results with those from the hospital laboratory, some patients get consistent results while others do not. The extent of this problem is unknown. Our study aimed to quantify the between-subject variation of the systematic PT-INR difference between CoaguChek and a hospital laboratory method. We used register data with PT-INR results from both CoaguChek and a hospital laboratory method (STA-SPA+) in samples taken simultaneously from 108 patients. After excluding five patients with outlying results, we used mixed-effects models to estimate individual slopes and intercepts to describe the systematic relationship between the two methods for each patient, and calculated the fraction of patients having a systematic difference greater than 0.3 INR units. The included 103 patients had from 3 to 16, median seven data pairs measured over a time span from 15 to 2319, median 234 days. The mean of individual slopes was 1.113, with a standard deviation of 0.137. Corresponding values for the intercept were -0.151 and 0.208, respectively. Adjusted for the average systematic difference, the proportion of patients with a systematic difference greater than 0.3 INR units increased from 15% at a PT-INR level of 2.5 to 50% at a PT-INR level of 4. The systematic difference between CoaguChek and STA-SPA + varies considerably between patients. This precludes using a single, common formula to make the CoaguChek results directly comparable to the results from the hospital laboratory.

Measuring calprotectin in plasma and blood with a fully automated turbidimetric assay.

Calprotectin in plasma and blood might prove to be a useful biomarker of inflammation and infection; however, automated methods for analysing the concentration of calprotectin in those materials are lacking. We have validated a fully automated turbidimetric method and present health-related reference limits. Calprotectin was measured by Siemens Advia XPT with the Bühlmann fCAL® turbo test (Bühlmann Laboratories AG, Schönenbuch, Switzerland), a particle enhanced turbidimetric immunoassay for quantification of calprotectin in fecal extracts. Plasma and serum samples were analysed directly, while whole blood was first extracted with M-PER® Mammalian Protein Extraction Reagent (ThermoFisher) and diluted with B-CAL-EX (Bühlmann). We studied analytical imprecision, estimated health-related reference limits and examined the correlation between neutrophil-calprotectin (blood-calprotectin adjusted for plasma-calprotectin) and the neutrophil count. The intermediate ('day-to-day') coefficient of variation was 3.5 and 1.0% for heparin-plasma-calprotectin at 0.52 mg/L and 3.53 mg/L, respectively, and 4.9% for heparin-blood-calprotectin at 50.2 mg/L. Health-related reference limits were 0.470-3.02 mg/L for calprotectin in heparin-plasma, 50.8-182 mg/L for calprotectin in heparin-blood, 0.534-2.41% for the ratio between them and 24.7-33.3 pg for the mean amount of calprotectin per neutrophil. Compared to heparin-plasma, calprotectin concentrations were significantly lower in EDTA-plasma and higher in serum (p < .05). Correlation between neutrophil-calprotectin and the neutrophil count was excellent. We have shown that the Bühlmann fCAL® turbo test can be used to measure calprotectin in plasma and blood.