Quantitative Assessment of Multiorgan Sequestration of Parasites in Fatal Pediatric Cerebral Malaria.

Children in sub-Saharan Africa continue to acquire and die from cerebral malaria, despite efforts to control or eliminate the causative agent, Plasmodium falciparum. We present a quantitative histopathological assessment of the sequestration of parasitized erythrocytes in multiple organs obtained during a prospective series of 103 autopsies performed between 1996 and 2010 in Blantyre, Malawi, on pediatric patients who died from cerebral malaria and controls. After the brain, sequestration of parasites was most intense in the gastrointestinal tract, both in patients with cerebral malaria and those with parasitemia in other organs. Within cases of histologically defined cerebral malaria, which includes phenotypes termed "sequestration only" (CM1) and "sequestration with extravascular pathology" (CM2), CM1 was associated with large parasite numbers in the spleen and CM2 with intense parasite sequestration in the skin. A striking histological finding overall was the marked sequestration of parasitized erythrocytes across most organs in patients with fatal cerebral malaria, supporting the hypothesis that the disease is, in part, a result of a high level of total-body parasite sequestration.

A histological method for quantifying Plasmodium falciparum in the brain in fatal paediatric cerebral malaria.

BACKGROUND: The sequestration of Plasmodium falciparum-infected erythrocytes in brain microvasculature through cytoadherence to endothelium, is the hallmark of the definitive diagnosis of cerebral malaria and plays a critical role in malaria pathogenesis. The complex pathophysiology, which leads each patient to the final outcome of cerebral malaria, is multifaceted and thus, metrics to delineate specific patterns within cerebral malaria are needed to further parse patients. METHODS: A method was developed for quantification utilizing counts of capillary contents (early-stage parasites, late-stage parasites and fibrin) from histological preparations of brain tissue after death, and compared it to the standard approach, in which the percentage of parasitized vessels in cross-section is determined. RESULTS: Within the initial cohort of 50 patients, two different observers agreed closely on the percentage of vessels parasitized, pigmented parasites and pigment globules (ICC = 0.795-0.970). Correlations between observers for correct diagnostic classification were high (Kendall's tau-b = 0.8779, Kappa = 0.8413). When these methods were applied prospectively to a second set of 50 autopsy samples, they revealed a heterogeneous distribution of sequestered parasites in the brain with pigmented parasites and pigment globules present in the cerebellum > cortex > brainstem. There was no difference in the distribution of early stages of parasites or in the percentage of vessels parasitized across the same sites. The second cohort of cases was also used to test a previously published classification and regression tree (CART) analysis; the quantitative data alone were able to accurately classify and distinguish cerebral malaria from non-cerebral malaria. Classification errors occurred within a subclassification of cerebral malaria (CM1 vs CM2). A repeat CART analysis for the second cohort generated slightly different classification rules with more accurate subclassification, although misclassification still occurred. CONCLUSIONS: The traditional measure of parasite sequestration in falciparum malaria, the percentage of vessels parasitized, is the most reliable and consistent for the general diagnosis of cerebral malaria. Methods that involve quantitative measures of different life cycle stages are useful for distinguishing patterns within the cerebral malaria population; these subclassifications may be important for studies of disease pathogenesis and ancillary treatment.

Supraorbital postmortem brain sampling for definitive quantitative confirmation of cerebral sequestration of Plasmodium falciparum parasites.

BACKGROUND: The conventional clinical case definition of cerebral malaria (CM) is imprecise but specificity is improved by a definitive clinical feature such as retinopathy or confirming sequestration of parasites in a post-mortem examination of the brain. A full autopsy is often not possible, since it is costly and may encounter resistance of the deceased's family. METHODS: We have assessed the use of a cytological smear of brain tissue, obtained post-mortem by supraorbital sampling, for the purpose of quantifying cerebral sequestration in children with fatal malaria in Blantyre, Malawi. We have compared this method to histological quantification of parasites at autopsy. RESULTS: The number of parasites present on cytological smears correlated with the proportion of vessels parasitized as assessed by histology of fixed and stained brain tissue. Use of cytological results in addition to the standard clinical case definition increases the specificity of the clinical case definition alone from 48.3% to 100% with a minimal change in sensitivity. CONCLUSIONS: Post-mortem supraorbital sampling of brain tissue improves the specificity of the diagnosis of fatal cerebral malaria and provides accurate quantitative estimates of cerebral sequestration. This tool can be of great value in clinical, pathogenetic, and epidemiological research studies on cerebral malaria.

The Association between Insurance Status and Acceptance of Chlamydia Screening By Teenagers Who Present for Preventive Care Visits.

STUDY OBJECTIVE: The purpose of this study was to evaluate whether providers offer chlamydia screening to teenagers and/or whether screening is accepted at different rates depending on insurance type. DESIGN: Retrospective chart review. SETTING: Academic center serving urban and suburban patients between April 2009 and October 2011. PARTICIPANTS: Nine hundred eighty-three health maintenance visits for asymptomatic, insured female adolescents aged 15-19 years. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Dichotomous dependent variables of interest indicated whether chlamydia screening was: (1) offered; and (2) accepted. The key independent variable insurance type was coded as 'public' if Medicaid or Medicaid Managed Care and 'private' if a commercial plan. χ(2) and logistic regression analyses were used to assess the significance of differences in screening rates according to insurance type. RESULTS: Of asymptomatic health-maintenance visits 933 (95%) had a documented sexual history and 339 (34%) had a documented history of sexual activity. After excluding those who had a documented chlamydia screen in the 12 months before the visit (n = 79; 23%), 260 visits met eligibility for chlamydia screening. Only 169 (65%) of eligible visits had chlamydia screening offered and there was no difference in offer of screening according to insurance type. Significantly more visits covered by public insurance had chlamydia screening accepted (98%) than those covered by private insurance (82%). Controlling for demographic factors, the odds of accepted chlamydia screening was 8 times higher in visits covered by public insurance than those with private insurance. CONCLUSION: Although publically and privately insured teens were equally likely to be offered chlamydia screening, publically insured teens were significantly more likely to accept screening. Future research should investigate reasons for this difference in screening acceptance. These findings have implications for interventions to improve chlamydia screening because more adolescents are covered by parental insurance under the Affordable Care Act.