Prevalence of factor VIII inhibitors among Afghan patients with hemophilia A: a first report

: Prevalence of inhibitors in Afghan hemophilia patients has not been reported previously. Our aim was to determine the prevalence of factor VIII inhibitors among hemophilia A patients from the Kabul province of Afghanistan to identify and characterize the pattern of inhibitor formation. Clinical information and blood samples were collected from three hemophilia centers in Kabul, Afghanistan. Plasma samples were obtained from 62 patients with severe (80.5%) and 15 patients with moderate hemophilia A (19.5%) in this cross-sectional study design. All the patients were receiving on-demand treatment. The Nijmegen modification of the Bethesda assay was used to detect inhibitors. Multiplex PCR, inverse-PCR, Multiplex ligation-dependent probe amplification and direct sequencing were performed for genotyping. Inhibitor activity was detected in one out of 15 (6.7%) patients with moderate hemophilia and in six out of 62 (9.7%) with severe disease. Apart from the intron 22 inversion, five different mutations including one missense, two large and two small deletions were detected. This is the first report showing that the prevalence of inhibitors in Afghan hemophilia A patients is much lower than in other populations.

Can the diagnostic reliability of the thrombin generation test as a global haemostasis assay be improved? The impact of calcium chloride concentration

BACKGROUND

Thrombin generation test (TGT) is a global haemostasis assay with a potential to predict bleeding tendencies and treatment effects in patients with haemophilia. Despite 15 years of clinical research, the diagnostic value of TGT remains controversial, possibly due to suboptimal sensitivity to coagulation deficiencies, robustness and reproducibility.

OBJECTIVE

The goal of this study was to explore the effect of calcium chloride (CaCl₂ ) concentration on the TGT's response to intrinsic coagulation factors (F) VIII, IX and XIa.

METHODS

Normal and factor-deficient plasmas supplemented with lacking coagulation factor and different CaCl₂ levels were tested by calibrated thrombinography assay.

RESULTS

Thrombin peak height (TPH) was strongly CaCl₂ dependent, increasing sharply from no TG at 5 mm to a peak at 13.8 mm of CaCl₂ (95% confidence interval [CI]: 13.0, 14.5) in normal and normalized deficient plasmas and at 11.9 mm (CI: 9.7, 14.2) in deficient plasmas, and then decreasing slowly to a complete inhibition at 30-40 mm. In contrast, TG lag time, time to peak and endogenous thrombin potential were nearly insensitive to CaCl₂ concentrations between 10 and 20 mm. The maximal difference between the TPH in deficient and supplemented plasmas was observed at 15.5 mm (CI: 12.8, 18.1).

CONCLUSION

Variations in CaCl₂ concentration in the assay mixture and sodium citrate concentrations in patient plasma samples may affect TGT responses, sensitivity and result in increased inter- and intra-laboratory variance. Implementation of TGT by clinical and quality control laboratories may require optimization of CaCl₂ concentration.