Correcting mortality for loss to follow-up: a nomogram applied to antiretroviral treatment programmes in sub-Saharan Africa

Background The World Health Organization estimates that in sub-Saharan Africa about 4 million HIV-infected patients had started antiretroviral therapy (ART) by the end of 2008. Loss of patients to follow-up and care is an important problem for treatment programmes in this region. As mortality is high in these patients compared to patients remaining in care, ART programmes with high rates of loss to follow-up may substantially underestimate mortality of all patients starting ART. Methods and Findings We developed a nomogram to correct mortality estimates for loss to follow-up, based on the fact that mortality of all patients starting ART in a treatment programme is a weighted average of mortality among patients lost to follow-up and patients remaining in care. The nomogram gives a correction factor based on the percentage of patients lost to follow-up at a given point in time, and the estimated ratio of mortality between patients lost and not lost to follow-up. The mortality observed among patients retained in care is then multiplied by the correction factor to obtain an estimate of programme-level mortality that takes all deaths into account. A web calculator directly calculates the corrected, programme-level mortality with 95% confidence intervals (CIs). We applied the method to 11 ART programmes in sub-Saharan Africa. Patients retained in care had a mortality at 1 year of 1.4% to 12.0%; loss to follow-up ranged from 2.8% to 28.7%; and the correction factor from 1.2 to 8.0. The absolute difference between uncorrected and corrected mortality at 1 year ranged from 1.6% to 9.8%, and was above 5% in four programmes. The largest difference in mortality was in a programme with 28.7% of patients lost to follow-up at 1 year. Conclusions The amount of bias in mortality estimates can be large in ART programmes with substantial loss to follow-up. Programmes should routinely report mortality among patients retained in care and the proportion of patients lost. A simple nomogram can then be used to estimate mortality among all patients who started ART, for a range of plausible mortality rates among patients lost to follow-up.

Mean CD4 cell count changes in patients failing a first-line antiretroviral therapy in resource-limited settings

Background Changes in CD4 cell counts are poorly documented in individuals with low or moderate-level viremia while on antiretroviral treatment (ART) in resource-limited settings. We assessed the impact of on-going HIV-RNA replication on CD4 cell count slopes in patients treated with a first-line combination ART. Method Naïve patients on a first-line ART regimen with at least two measures of HIV-RNA available after ART initiation were included in the study. The relationships between mean CD4 cell count change and HIV-RNA at 6 and 12 months after ART initiation (M6 and M12) were assessed by linear mixed models adjusted for gender, age, clinical stage and year of starting ART. Results 3,338 patients were included (14 cohorts, 64% female) and the group had the following characteristics: a median follow-up time of 1.6 years, a median age of 34 years, and a median CD4 cell count at ART initiation of 107 cells/μL. All patients with suppressed HIV-RNA at M12 had a continuous increase in CD4 cell count up to 18 months after treatment initiation. By contrast, any degree of HIV-RNA replication both at M6 and M12 was associated with a flat or a decreasing CD4 cell count slope. Multivariable analysis using HIV-RNA thresholds of 10,000 and 5,000 copies confirmed the significant effect of HIV-RNA on CD4 cell counts both at M6 and M12. Conclusion In routinely monitored patients on an NNRTI-based first-line ART, on-going low-level HIV-RNA replication was associated with a poor immune outcome in patients who had detectable levels of the virus after one year of ART.

Mortality of HIV-infected patients starting antiretroviral therapy in sub-Saharan Africa: comparison with HIV-unrelated mortality

BACKGROUND: Mortality in HIV-infected patients who have access to highly active antiretroviral therapy (ART) has declined in sub-Saharan Africa, but it is unclear how mortality compares to the non-HIV-infected population. We compared mortality rates observed in HIV-1-infected patients starting ART with non-HIV-related background mortality in four countries in sub-Saharan Africa. METHODS AND FINDINGS: Patients enrolled in antiretroviral treatment programmes in Côte d'Ivoire, Malawi, South Africa, and Zimbabwe were included. We calculated excess mortality rates and standardised mortality ratios (SMRs) with 95% confidence intervals (CIs). Expected numbers of deaths were obtained using estimates of age-, sex-, and country-specific, HIV-unrelated, mortality rates from the Global Burden of Disease project. Among 13,249 eligible patients 1,177 deaths were recorded during 14,695 person-years of follow-up. The median age was 34 y, 8,831 (67%) patients were female, and 10,811 of 12,720 patients (85%) with information on clinical stage had advanced disease when starting ART. The excess mortality rate was 17.5 (95% CI 14.5-21.1) per 100 person-years SMR in patients who started ART with a CD4 cell count of less than 25 cells/microl and World Health Organization (WHO) stage III/IV, compared to 1.00 (0.55-1.81) per 100 person-years in patients who started with 200 cells/microl or above with WHO stage I/II. The corresponding SMRs were 47.1 (39.1-56.6) and 3.44 (1.91-6.17). Among patients who started ART with 200 cells/microl or above in WHO stage I/II and survived the first year of ART, the excess mortality rate was 0.27 (0.08-0.94) per 100 person-years and the SMR was 1.14 (0.47-2.77). CONCLUSIONS: Mortality of HIV-infected patients treated with combination ART in sub-Saharan Africa continues to be higher than in the general population, but for some patients excess mortality is moderate and reaches that of the general population in the second year of ART. Much of the excess mortality might be prevented by timely initiation of ART.

Searching the Rhone delta channel in Lake Geneva since François‐Alphonse Forel

In the late 19th century, F.A. FOREL led investigations of the Rhone River delta area of Lake Geneva that resulted in the dis- covery of a textbook example of a river-fed delta system containing impressive subaquatic channels. Well ahead of the marine counterparts, scientific observations and interpretations of water currents shaping the delta edifice for the first time documented how underflow currents carry cold, suspension-laden waters from the river mouth all the way to the deep basin. These early investigations of the Rhone delta laid the basis for follow-up studies in the 20th and 21th centuries. Sediment coring, water-column measurements, manned submersible diving, seismic reflection profiling and bathymetric sur- veying eventually provided a rich database to unravel the key erosional and depositional processes, further documenting the impact of human-induced changes in the catchment. With the merging of old and new scientific knowledge, today a comprehensive understanding prevails of how a delta changes through time, how its channels are formed, and what potential natural hazards may be related to its evolution. New and efficient bathymetric techniques, paired with novel coring operations, provided a time-series of morphologic evolution showing and quantifying the high dynamics of the delta/channel evolution in an unprecedented temporal and spatial reso- lution. Future investigations will continue to further quantify these dynamic processes and to link the evolution of the subaquatic domain with changes and processes in the catchment and with natural hazards. Its size, easy access, and large variety of states and processes will continue to make the Rhone delta area a perfect ‘laboratory’ in which general processes can be studied that could be upscaled or downscaled to other marine and lacustrine deltas.