Somsak Lolekha

Protective efficacy of hepatitis B vaccine without HBIG in infants of HBeAg-positive carrier mothers in Thailand ☆

The primary objective of this study was to estimate the efficacy of a recombinant hepatitis B vaccine (H-B-VAXII) in preventing chronic hepatitis B infection when given alone without concomitant hepatitis B immune globulin (HBIG) to healthy Thai infants born of HBeAg-positive carrier mothers. The infants received a 0.5 ml (5 micro g HBsAg) intramuscular injection of H-B-VAXII either at birth, 1, and 6 months of age (Schedule A) or at birth, 1, 2, and 12 months of age (Schedule B). Blood drawings for the determination of hepatitis B virus (HBV) serologic markers were scheduled 4, 9, and 13 months following the initial dose of vaccine. At 13 months, 5 (10%) of 50 infants vaccinated on Schedule A and 7 (14.9%) of 47 infants vaccinated on Schedule B had experienced chronic HBV infection. Based on an expected infection rate in unimmunized infants of either 70 or 90%, the overall efficacy for both schedules combined was estimated to be 82.3% (95% CI: 70.6, 90.6) or 86.2% (95% CI: 77.1, 92.7), respectively. Corresponding schedule-specific estimates were for Schedule A: 85.7% (95% CI: 68.8, 95.3) or 88.9% (95% CI: 75.8, 96.3) and for Schedule B: 78.7% (95% CI: 59.6, 91.1) or 83.4% (95% CI: 68.6, 93.1). These results suggest that in areas of high endemicity, where mothers may not always be screened for HBV infection, routine vaccination of infants at birth with a course of hepatitis B vaccine alone should be highly protective, even for very high-risk infants of HBeAg-positive mothers.

Update on value of the anion gap in clinical diagnosis and laboratory evaluation

Anion gap (AG) is a calculated value commonly used in clinical practice. It approximates the difference between the concentration of unmeasured anions (UA) and unmeasured cations (UC) in serum. At present, the reference range of anion gap has been lowered from 8-16 to 3-11 mmol/l because of the changes in technique for measuring electrolyte. However, clinicians and textbooks still refer and use the old reference value of 8-16 mmol/l. This may lead to misinterpretation of the value of anion gap. Our study updated the value of anion gap in clinical diagnosis and laboratory evaluation. Criteria for using anion gap were also suggested. We analyzed serum electrolyte using the Beckman Synchron CX5. The anion gap was calculated from the formula: [Na(+)-(Cl(-)+HCO(3)(-))]. We estimated the reference range using the non-parametric percentile estimation method. The reference range of anion gap obtained from 124 healthy volunteers was 5-12 mmol/l, which was low and confirmed the reports from other studies (3-11 mmol/l) using ion-selective electrode. From the retrospective study on the 6868 sets of serum electrolyte among hospitalized patients, we found the incidences of normal, increased, and decreased anion gaps were 59.5%, 37.6%, and 2.9%, respectively. The mean and central 90% range of increased anion gap were 16 and 13-20 mmol/l, which was lower than those reported in previous study (25 and 19-28 mmol/l). Anion gap exceeding 24 mmol/l was rare. The mean and central 90% range of decreased anion gap were 3 and 2-4 mmol/l, which were lower than those reported in previous study (6 and 3-8 mmol/l). The value of less than 2 mmol/l was rare. The most common causes of increased anion gap (hypertensive disease, chronic renal failure, malignant neoplasms, diabetes mellitus and heart diseases) and decreased anion gap (liver cirrhosis and nephrotic syndrome) in this study were similar to those in previous studies. We found two cases of IgG multiple myeloma with anion gap of 2 mmol/l. In conclusion, clinicians and laboratorians can use the anion gap as clue in quality control. They can check the incidences of increased and decreased anion gap. If one finds high incidence of increased anion gap (>24 mmol/l) or decreased anion gap (<2 mmol/l), one should check the quality control of electrolyte and whether the patients were hypoalbuminemia or hyperglobulinemia. An anion gap exceeding 24 mmol/l will suggest the presence of metabolic acidosis. It is very rare to find anion gap with the negative sign.

Immunogenicity and Safety of Two Doses of a Paediatric Hepatitis A Vaccine in Thai Children: Comparison of Three Vaccination Schedules

As fewer children in Thailand are exposed to hepatitis A virus (HAV) and so do not have seroprotective anti-HAV antibodies, they are becoming an important source of HAV transmission. A flexible HAV vaccination schedule would facilitate incorporation of the vaccine into existing immunization programmes, and we compared the immunogenicity and safety of three HAV immunization schedules. An open, randomized, clinical trial was carried out in which healthy children were given a primary dose of the inactivated hepatitis A vaccine, Avaxim 80 paediatric, with a booster dose 6, 12 or 18 months later. Anti-HAV geometric mean concentrations (GMC), seroconversion rates, and GMC ratios (GMCR) of the three schedules were compared and reactogenicity was evaluated. Seroconversion rates were above 98 per cent (per group) up to the booster. The three schedules were equivalent in terms of GMCRs, each eliciting a large booster effect. Local reactions were reported for fewer than 9 per cent of each group after dose one and less frequently after the booster dose. Injection site pain, gastrointestinal tract disorders and fever were the most commonly reported adverse events. No vaccine-related serious adverse events were reported. It was concluded that the hepatitis A vaccine, Avaxim 80 paediatric, is safe and immunogenic when given as a two-dose schedule to healthy seronegative children aged 5-10 years, with the second dose given at either 6, 12 or 18 months after the first.

Comparison of the Performance of Point-of-Care and Device Analyzers to Hospital Laboratory Instruments

Point-of-care testing plays an important role in critical care medicine. This study evaluated the performance of the OPTI CCA and OMNI 9 critical care analyzers by comparing them to our currently used routine instruments (Stat Profile Ultra C, CRT, Dimension RxL, and Cell Dyn). The authors used least squares linear regression, the correlation coefficient, mean bias, and Student t test for data analysis. Three levels of aqueous control material were used to perform within-run and between-day evaluation of imprecision, as well as recovery studies, and arterial whole-blood and plasma obtained from critically ill patients were used to perform the comparison study. For within-run and between-day imprecision, the coefficients of variation of analyte measurements obtained with the OPTI and OMNI were within acceptable limits, and the recovery of analytes was close to 100%. Most comparison results from the OPTI and OMNI correlated well with results from currently used routine instruments. Most analytes on the OPTI and OMNI showed acceptable agreement with small mean biases, except pO2, Na , and Cl. Therefore, users should check these analytes and consider the potential clinical significance of such bias. Otherwise, the OPTI CCA and the OMNI 9 are suitable for analysis of samples from patients in critical care.