Diagnostic Tests for Hypofibrinogenemia Resulting from Green Pit Viper (Trimeresurus albolabris) Envenomation: A Simulated In Vitro Study.

INTRODUCTION: The green pit viper (GPV) Trimeresurus albolabris is found in Southeast Asia. Its venom has a thrombin-like activity that can cause hypofibrinogenemia. Fibrinogen measurement is not always available. We aimed to establish a more available diagnostic tool indicating hypofibrinogenemia caused by GPV envenomation. METHODS: This was an in vitro study, in which healthy subjects aged 20 to 45 y were enrolled. There were 2 experiments. In Experiment 1, blood samples from 1 subject had varying amounts of T albolabris venom added to determine its effect on the fibrinogen level (FL). In Experiment 2, 3 sets of blood samples were obtained from another 25 subjects. The 2 venom doses established in Experiment 1 were used on 2 sets of the samples to simulate severe (FL <1.0 g·L-1) and mild hypofibrinogenemia (FL 1.0-1.7 g·L-1). The third set of samples was venom-free. All samples were used for platelet counts, prothrombin time (PT)/international normalized ratio (INR)/activated partial thromboplastin time (aPTT), and 2 bedside clotting tests. Diagnostic parameters were calculated against the target FL of <1.0 g·L-1 and <1.7 g·L-1. RESULTS: Twenty-five subjects were enrolled in Experiment 2. On referencing normal cutoff values (platelet count >150,000 cells/mm3, venous clotting time <15 min, normal 20-min whole blood clotting time, INR <1.2, aPTT <30), we found abnormalities of 5, 0, 0, 3, and 22%, respectively. The highest correlation with hypofibrinogenemia was provided by PT/INR. For an FL of <1.0 g·L-1, PT and INR revealed the highest areas under the receiver operating characteristic curve, 0.76 (95% CI, 0.55-0.97) and 0.76 (95% CI, 0.57-0.97), respectively. The highest accuracy and the highest sensitivity were provided by PT/INR. CONCLUSIONS: PT/INR could be used as a diagnostic test for severe hypofibrinogenemia in GPV envenomation because of its high accuracy and area under the receiver operating characteristic curve.

Incidence and risk factors of iron deficiency anemia in term infants.

OBJECTIVE: To compare the incidence of iron deficiency anemia (IDA) between breast-fed (BF) and formula-fed (FF) infants and to identify the risk factors of IDA in these infants. DESIGN: Cohort study. MATERIAL AND METHOD: A study of 140 full- term infants (70 BF and 70 FF) was conducted at BMA Medical College and Vajira Hospital from February 2002 to November 2003. All infants were followed at the age of 1, 2, 4, 6, 9 and 12 months for growth and developmental assessment. Blood samples were analyzed for hemoglobin (Hb), hematocrit (Hct) and mean corpuscular volume (MCV) at 9 - 12 months; and infants with Hb < 11.0 g/dl were further investigated for the cause of anemia. RESULTS: The mean values of Hb, Hct, MCV and serum ferritin of BF infants were 10.8 g/dl, 32.8%, 70.9fl and 16.7 ng/ml respectively, which were significantly lower than those of FF infants (11.4 g/dl, 35.1%, 73.3fl, and 36.9 ng/ml, p < 0. 05). Anemia was found in 27 BF infants (38.6%) compared with 10 FF infants (14.39%). The incidence of IDA in BF infants was significantly higher than FF infants (25.7% vs 2.9%, p < 0.001). Risk factors of IDA included low birth weight, breastfeeding and inadequate complementary food (adjusted RR (95% CI): 3.1(1.1 - 9.1), 6.3(1.5 - 25.0), 7.7(2.8 - 20.0), respectively). CONCLUSION: IDA is more prevalent in BF than FF infants. Risk factors of IDA are low birth weight, breastfeeding and inadequate complementary food. Prevention of IDA in infants should be achieved through adequate iron-rich complementary food and screening for Hb or Hct at 9 - 12 months of age in high risk infants.