To normalize or not?: Dilute Russell viper venom time testing.

OBJECTIVES: We conducted a comparison between the nonnormalized dilute Russell viper venom time (dRVVT) screen/confirm ratio (SCR) in patient plasma and the normalized SCR obtained using reference pooled plasma. The aim was to assess the impact of normalization on the lupus anticoagulant (LA) status in our patient population. METHODS: In our retrospective analysis, we included a total of 464 patients who underwent dRVVT testing. For those with positive screens, mixing studies were performed, followed by confirmatory testing. Additionally, the dRVVT of reference pooled plasma was measured. A positive conventional (nonnormalized) or normalized SCR was defined as an SCR greater than or equal to 1.2. RESULTS: In total, 5.6% (26) of the 464 samples tested were confirmed positive for LA by both methods, out of which 12 had a clinical history of thrombosis. Although a statistically significant difference between the 2 groups (P = .0096) was found, the magnitude of absolute mean SCR differences (bias) was 0.04 (2.51%). There was 100% concordance of testing results between the 2 groups. CONCLUSIONS: The lupus anticoagulant status by the dRVVT assay was not changed based on normalization. Normalization was of no clinical benefit in our patient population; therefore, there was no need for the extra calculation step. Normalization may be useful for intermethod and interlaboratory studies and not for within-method LA detection.

Comparison of the Alere i Strep A Test and the BD Veritor System in the Detection of Group A Streptococcus and the Hypothetical Impact of Results on Antibiotic Utilization.

Rapid detection of group A Streptococcus (GAS) is an integral component of treatment decisions in the clinic, especially in the pediatric population. We prospectively collected 216 specimens from symptomatic, predominantly pediatric patients and evaluated the performance of the Alere i Strep A test (Alere i; Alere Inc., Scarborough, ME) and the BD Veritor system (BD Veritor; Becton, Dickinson and Company, Sparks, MD), with culture results being used as a comparator. Real-time PCR (RT-PCR) was performed as an arbiter in discordant cases. Comprehensive chart review was also done to determine the hypothetical impact of the results on antibiotic use. Alere i had a sensitivity and a specificity of 100% and 91.3%, respectively, and BD Veritor had a sensitivity and a specificity of 76.2% and 93.6%, respectively, when the results were compared to those of GAS culture. Further analysis of discordant results using RT-PCR revealed that while BD Veritor missed 13 confirmed positive cases, Alere i detected 100% (n = 13) of the same cases. Analysis of assay agreement showed that Alere i and BD Veritor had only moderate agreement (agreement = 0.888 [95% confidence interval {CI}, 0.838 to 0.927]; kappa index = 0.689 [95% CI, 0.91 to 0.974]). We also found both the underutilization and the overutilization of antibiotics based on the results of molecular testing. Overall, Alere i showed superior performance over BD Veritor in the detection of GAS pharyngitis and could potentially assist in better antibiotic utilization.

Volume regulatory hormones and plasma volume in pregnant women with sickle cell disorder.

BACKGROUND: Sickle cell disease (haemoglobin SS (HbSS)) mainly affects those of West African origin and is associated with hypervolaemia. Plasma volume rises by up to 50% in normal pregnancy but was previously found to be paradoxically contracted in late sickle cell pregnancy. The renin-angiotensin-aldosterone system is activated very early in human pregnancy to support the plasma volume expansion. We hypothesised that activation of the renin-angiotensin-aldosterone system would be blunted in pregnant women with sickle cell disease. MATERIALS AND METHODS: We measured plasma volume and concentrations of plasma renin, angiotensinogen, aldosterone and other volume-related hormones in a cross-sectional study of pregnant and non-pregnant Nigerian women with HbSS or HbAA. RESULTS: Plasma volume was higher in non-pregnant HbSS than HbAA women, but had not risen by 16 weeks, unlike plasma volume in HbAA women. The concentration of plasma renin also rose significantly less by 16 weeks in HbSS; angiotensinogen and aldosterone concentrations increased. CONCLUSIONS: The lower plasma renin concentration at 16 weeks with HbSS could be either primary or secondary to vasoconstriction related to inadequate vasodilator activity. The contracted plasma volume might then stimulate aldosterone synthesis by non-angiotensin II dependent stimulation. Studies of vasodilators such as nitric oxide, vasodilator eicosanoids or the PlGF/VEGF/sFlT-1 axis in pregnant HbSS and HbAA women will test this hypothesis.

Impact of premature birth and critical illness on neonatal range of plasma amino acid concentrations determined by LC-MS/MS.

BACKGROUND: The number of newborns and the number of disorders detected by large-scale screening programs has increased dramatically in the last decade. Newborn screening is a multi-step process requiring confirmatory testing to establish and refine a diagnosis. Whereas screening cutoffs are established to detect all cases of a specific disease, confirmatory testing is performed against a backdrop of many co-morbid conditions and interpretation of results is often not straightforward. The goal of the current study was to define the range of amino acid concentrations encountered in normal, premature, and acutely ill newborns as an aid to the interpretation of follow-up testing for suspicious newborn screens. MATERIALS AND METHODS: Residual plasma samples from 354 neonates (age 1-10 days) were utilized. 206 samples were from neonates with uncomplicated birth histories and prompt hospital discharge. 98 specimens were derived from a population of children receiving intensive care with diagnoses that included sepsis, respiratory insufficiency, cardiac malfunction/malformation and gastrointestinal complications. 50 samples were from infants born after 32 but before 37 full weeks gestation that were discharged following uneventful hospital courses. 25 amino acids were quantitated by LC-MS/MS and reference intervals determined by non-parametric statistical methods. Distributions were compared using Kruskal-Wallis analyses for independent samples. RESULTS: The distributions of multiple amino acids in premature and critically ill infants were significantly different than those observed in healthy newborns. Differing distributions were found for phenylalanine, the branched chain amino acids, methionine, glutamine, glutamate, arginine, lysine, α-aminoadipic acid, and ß-aminoisobutyric acid. In most cases median values were increased and distributions more positively skewed in premature or ill newborns compared to healthy newborns. In addition, we report neonatal homocitrulline reference intervals for these newborn populations determined by an LC-MS/MS technique that is not confounded by methionine interference. CONCLUSION: These data provide a basis for improved detection of genetic metabolic disorders in newborns, particularly those born prematurely or with a variety of critical co-morbid conditions.

Exploratory study of plasma total homocysteine and its relationship to short-term outcome in acute ischaemic stroke in Nigerians.

BACKGROUND: Hyperhomocysteinemia is a potentially modifiable risk factor for stroke, and may have a negative impact on the course of ischaemic stroke. The role of hyperhomocysteinemia as it relates to stroke in Africans is still uncertain. The objective of this study was to determine the prevalence and short-term impact of hyperhomocysteinemia in Nigerians with acute ischaemic stroke. We hypothesized that Hcy levels are significantly higher than in normal controls, worsen stroke severity, and increase short-term case fatality rates following acute ischaemic stroke. METHODS: The study employed both a case-control and prospective follow-up design to study hospitalized adults with first - ever acute ischaemic stroke presenting within 48 hours of onset. Clinical histories, neurological evaluation (including National Institutes of Health Stroke Scale (NIHSS) scores on admission) were documented. Total plasma Hcy was determined on fasting samples drawn from controls and stroke cases (within 24 hours of hospitalization). Outcome at 4 weeks was assessed in stroke patients using the Glasgow Outcome Scale (GOS). RESULTS: We evaluated 155 persons (69 acute ischaemic stroke and 86 healthy controls). The mean age +/- SD of the cases was 58.8 +/- 9.8 years, comparable to that of controls which was 58.3 +/- 9.9 years (T = 0.32; P = 0.75). The mean duration of stroke (SD) prior to hospitalization was 43.5 +/- 38.8 hours, and mean admission NIHSS score was 10.1 +/- 7.7. Total fasting Hcy in stroke patients was 10.2 +/- 4.6 umol/L and did not differ significantly from controls (10.1 +/- 3.6 umol/L; P = 0.88). Hyperhomocysteinemia, defined by plasma Hcy levels > 90th percentile of controls (>14.2 umol/L in women and >14.6 umol/L in men), was present in 7 (10.1%) stroke cases and 11 (12.8%) controls (odds ratio 0.86, 95% confidence interval 0.31 - 2.39; P > 0.05). In multiple regression analysis admission NIHSS score (but not plasma Hcy) was a significant determinant of 4 week outcome measured by GOS score (P < 0.0001). CONCLUSION: This exploratory study found that homocysteine levels are not significantly elevated in Nigerians with acute ischaemic stroke, and admission Hcy level is not a determinant of short-term (4 week) stroke outcome.