Decreased oxygen availability at high altitude requires physiological adjustments allowing for adequate tissue oxygenation. One such mechanism is a slow increase in the hemoglobin concentration ([Hb]) resulting in elevated [Hb] in high-altitude residents. Diagnosis of anemia at different altitudes requires reference values for [Hb]. Our aim was to establish such values based on published data of residents living at different altitudes by applying meta-analysis and multiple regressions. Results show that [Hb]is increased in all high-altitude residents. However, the magnitude of increase varies among the regions analyzed and among ethnic groups within a region. The highest increase was found in residents of the Andes (1 g/dL/1000 m), but this increment was smaller in all other regions of the world (0.6 g/dL/1000 m). While sufficient data exist for adult males and females showing that sex differences in [Hb] persist with altitude, data for infants, children, and pregnant women are incomplete preventing such analyses. Because WHO reference values were originally based on [Hb] of South American people, we conclude that individual reference values have to be defined for ethnic groups to reliably diagnose anemia and erythrocytosis in high-altitude residents. Future studies need to test their applicability for children of different ages and pregnant women.

Background Cutibacterium species are common pathogens in periprosthetic joint infections (PJI). These infections are often treated with β-lactams or clindamycin as monotherapy, or in combination with rifampin. Clinical evidence supporting the value of adding rifampin for treatment of Cutibacterium PJI is lacking. Materials/methods In this multicenter retrospective study, we evaluated patients with Cutibacterium PJI. The primary endpoint was clinical success, defined by the absence of infection relapse or new infection within a minimal follow-up of 12 months. We used Fisher’s exact tests and Cox proportional hazards models to analyze the effect of rifampin and other factors on clinical success after PJI. Results We included 187 patients (72.2% male, median age 67 years) with a median follow-up of 36 months. The surgical intervention was two-stage exchange in 95 (50.8%), one-stage exchange in 51 (27.3%), debridement and implant retention (DAIR) in 34 (18.2%), and explantation without reimplantation in 7 (3.7%). Rifampin was included in the antibiotic regimen in 81 (43.3%) cases. Infection relapse occurred in 28 (15.0%), and new infection in 13 (7.0%) cases. In the time-to-event analysis, DAIR (adjusted HR=2.15, p=0.03) and antibiotic treatment over 6 weeks (adjusted HR=0.29, p=0.0002) significantly influenced treatment failure. We observed a tentative evidence for a beneficial effect of adding rifampin to the antibiotic treatment – though not statistically significant for treatment failure (adjusted HR=0.5, p=0.07) and not for relapses (adjusted HR=0.5, p=0.10). Conclusions We conclude that a rifampin combination is not markedly superior in Cutibacterium PJI but a dedicated prospective multicenter study is needed.

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