Reviews: Is the Calcium Correct? Measuring Serum Calcium in Dialysis Patients

Abnormalities in calcium concentration are frequent in patients receiving dialysis therapy. Most cases of both hypo‐ and hypercalcemia are mild and asymptomatic. There is concern, however, that, on the one hand, hypocalcemia can drive hyperparathyroidism and eventually lead to gland hypertrophy and autonomous function. Hypercalcemia, on the other hand, can be associated with increased extraosseous calcium and phosphate deposition leading to vascular calcification with an attendant mortality and morbidity. Calcium exists in three main forms in the blood: the physiologically active free or ionized fraction (terms often used interchangeably), a protein bound fraction, and a fraction complexed to other anions. Although the ionized calcium can readily be measured using ion‐specific electrodes, it is the total calcium that is most commonly measured because of sample handling and cost concerns. As it is the free or ionized form that is biologically active (and therefore of most relevance), a number of adjustment formulae have been derived to “correct” the total calcium for changes in albumin, protein, and complexing ion concentrations. These formulae show good statistical correlation with measured ionized calcium in populations studied as a whole, but are generally poor predictors of true ionized hypo‐ or hypercalcemia in individual patients. International guideline committees in nephrology recommend frequent assessment of calcium levels in dialysis patients and recommend that these levels be kept within the normal reference range. These guidelines are less clear on which measurement of calcium should be used to guide clinical decision making. This review examines the merits of making any adjustment to the total calcium measurement, and suggests when it is appropriate to measure the ionized or free calcium.     

Unique Aspects of the Care of HIV-Positive Latino Patients Living in the United States

Latinos are disproportionately affected by HIV, with a higher risk of infection and a delayed presentation to care as compared to non-Hispanic whites. Over the last decade many Latinos, especially foreign-born migrants, have settled in regions of the country with historically low Latino representation. Therefore, clinicians who care for HIV-infected patients are likely to encounter Latino patients, regardless of their practice location. Providing optimal care to this population may be especially challenging for clinicians practicing in areas of newer Latino expansion, where culturally appropriate services may be sparse. In this article, we argue that an understanding of the HIV epidemic among Latinos requires an appreciation of the diversity and heterogeneity of the Latino population in the United States. We also review unique clinical aspects of HIV care among Latinos, including manifestation of co-infections with pathogens endemic in Latin America but rare in the United States.     

Functional analysis of the CD8+CD57+ cell population in normal healthy individuals and matched unrelated T-cell-depleted bone marrow transplant recipients

The biological activities of CD8+ that co-express CD57 remain poorly defined. It is unclear whether all CD8+ cells have the potential to become CD57+ or whether they represent a unique subset with distinct functions. Several studies have reported the association between elevated numbers of CD8+CD57+ and a wide range of clinical disorders such as viral reactivation of human cytomegalovirus (HCMV). In this study, we have investigated the relationship between viral reactivation and the effect of diminished interleukin (IL)-2 production. Using CD8+ cells isolated from patients at various times after allogeneic transplants and in vitro models of HCMV infection, we determined their combined effect on CD8+CD57+. Our results show that high numbers of CD8+CD57+ correlated with diminished killing of HCMV-infected targets. In addition, we showed a synergistic effect between IL-2 and HCMV in the expansion of CD8+CD57+ cells. Furthermore, these cells after anti-CD3 stimulation did not produce tumour necrosis factor (TNF)-alpha or interferon (IFN)-gamma. Interestingly, IL-10 production was elevated in several patients which appeared to be associated with the time from transplant.     

Early Onset Neonatal Group B Streptococcus (GBS) Infection: Associated Obstetric Risk Factors

An analysis of all early onset neonatal Group B streptococcal (GBS) infections at the Royal Women's Hospital, Melbourne was made for the 10-year period 1979-1988. There were 104 cases with 29 neonatal deaths (28%). One or more predisposing perinatal risk factors was evident in 82% of cases (premature labour 79%, prolonged membrane rupture (greater than 12 hours) 57%, premature rupture of the membranes 69%, maternal sepsis 29%). Overall, 88% of GBS infections were evident within 24 hours of birth, suggesting an intrapartum pathogenesis for infection.     

Trends in mortality in children hospitalized with meningococcal infections, 1957 to 1987

We reviewed charts of 261 children seen at Children's Hospital of Wisconsin from 1957 to 1987 with culture-proven meningococcemia or meningococcal meningitis, and we analyzed trends in mortality and disease severity for that interval. Overall case fatality was 10%, ranging from 9% in the period 1957 to 1963, to 16% in the period 1980 to 1987 (P = 0.15). The percent of patients admitted with severe disease increased from 14% to 38% (P = 0.001). When stratified by disease severity, case-fatality rates did not change with time. We conclude that technologic advances of the past 30 years had no measurable impact on mortality from meningococcal infection in our hospital and that crude case-fatality rates can be misleading if disease severity is not considered.     

Obstetric factors and relative risk of neonatal germinal layer/intraventricular hemorrhage

One hundred fifty-five inborn infants with a birth weight <- 1,500 gm were prospectively evaluated for germinal layer/intraventricular hemorrhage. Maternal characteristics, obstetric factors, and neonatal condition in the immediate newborn period were analyzed as possible risk factors for germinal layer/intraventricular hemorrhage. Early germinal layer/intraventricular hemorrhage or hemorrhages identified during the first 24 hours of life were observed in 85 (55%) of these infants. Another 37 (24%) had germinal layer/intraventricular hemorrhage after 24 hours of age (late germinal layer/intraventricular hemorrhage). None of the maternal and obstetric variables, including labor, mode of delivery, and presentation, appeared to increase the risk of germinal layer/intraventricular hemorrhage. The immediate neonatal condition, birth weight, gestational age, and intrauterine growth, all influenced the occurrence of germinal layer/intraventricular hemorrhage, especially early germinal layer/intraventricular hemorrhage. We suggest that future studies to investigate the role of maternal or obstetric factors in the pathogenesis of germinal layer/intraventricular hemorrhage should discriminate early from late germinal layer/intraventricular hemorrhage. Obstetric factors are more likely to influence the early onset of germinal layer/intraventricular hemorrhage; their effect, if any, becomes less discernible later.     

Physical activity, body mass index, and ovulatory disorder infertility

Few studies have examined whether activity and adiposity levels typical of American women affect their risk of ovulatory disorder infertility, and none has examined moderate and vigorous intensity exercise separately. We investigated these associations in the Nurses' Health Study II, comparing prospectively collected data on adiposity and activity for 830 cases of incident ovulatory infertility and 26,125 pregnancies. We observed a U-shaped association between body mass index (BMI) and relative risk of ovulatory infertility, with increased risk for BMI below 20.0 or above 24.0 kg/m2. On the basis of the BMI distribution of U.S. women, these findings suggest that 12% (95% confidence interval = 7-20%) of ovulatory infertility in the U.S. may be attributable to underweight (BMI <20.0) and 25% (95% CI = 20-31%) to overweight (BMI > or = 25.0). An increase in vigorous activity (but not moderate activity) was associated with reduced relative risk of ovulatory infertility. Each hour per week of vigorous activity was associated with a 7% (95% CI = 4-10%) lower relative risk of ovulatory infertility. After adjustment for BMI, a 5% (95% CI = 2-8%) reduction in relative risk per hour of weekly activity remained. These data suggest that, among American women, more ovulatory infertility is attributable to overweight and a sedentary lifestyle than to underweight and overexertion.