Nickel is the most frequent cause of contact allergy worldwide and has been studied extensively. This clinical review provides an updated overview of the epidemiology, exposure sources, methods for exposure quantification, skin deposition and penetration, immunology, diagnosis, thresholds for sensitization and elicitation, clinical pictures, prevention, and treatment. The implementation of a nickel regulation in Europe led to a decrease in the prevalence of nickel allergy, and changes in the clinical picture and disease severity. Nevertheless, the prevalences of nickel allergy in the European general population are approximately 8% to 19% in adults and 8% to 10% in children and adolescents, with a strong female predominance. Well‐known consumer items such as jewellery and metal in clothing are still the main causes of nickel allergy and dermatitis, although a wide range of items for both private and occupational use may cause dermatitis. Allergic nickel dermatitis may be localized to the nickel exposure site, be more widespread, or present as hand eczema. Today, efficient methods for exposure quantification exist, and new insights regarding associated risk factors and immunological mechanisms underlying the disease have been obtained. Nevertheless, questions remain in relation to the pathogenesis, the persistent high prevalence, and the treatment of severe cases.

Background: Although the prevalence of HIV-infection among individuals ≥50 years of age has increased, the impact of HIV-infection on risk of death in this population remains to be established. Our aim was to estimate long-term mortality among HIV-infected individuals who were 50 years or older, when compared with an individually-matched cohort from the background population. Methods: Population-based cohort-study including HIV-infected individuals ≥50 years, who were alive 1 year after HIV-diagnosis (n = 2440) and a comparison cohort individually-matched by age and gender extracted from the background population (n = 14,588). Cumulative survival was evaluated using Kaplan–Meier method and Mortality Rate Ratios (MRRs) were estimated using Cox Regression Models. Study period 1996–2014. Results: Estimated median survival time from age 50 years for HIV-infected individuals increased from 11.8 years (95% CI: 10.2 to 14.5) during 1996–1999 to 22.8 years (20.0–24.2) in 2006–2014. MRR decreased with increasing age from 3.8 (3.1–4.7) for 50–55 years to 1.6 (1.0–2.6) for 75–80 years. In a cohort of well-treated HIV-infected individuals ≥50 years without AIDS-defining events or comorbidity at study inclusion (n = 517). MRR was 1.7 (1.2–2.3) compared with population controls without comorbidity. Conclusion: Among HIV-infected individuals estimated median survival time from age 50 years has increased by more than 10 years from 1996–1999 to 2006–2014, but is still substantially lower than in the background population. Even among well-treated HIV-infected individuals ≥50 years without comorbidity or AIDS-defining events the estimated median survival time remains lower than in the general population.

The DHCS is a cohort of all HIV-infected individuals seen in one of the eight Danish HIV centres after 31 December 1994. Here we update the 2009 cohort profile emphasizing the development of the cohort. Every 12-24 months, DHCS is linked with the Danish Civil Registration System (CRS) in order to extract an age- and sex-matched comparison cohort from the general population, as well as cohorts of family members of the HIV-infected patients and of the comparison cohort. The combined cohort is linked with CRS, the Danish Cancer Registry, the Danish National Hospital Registry, the Danish Registry of Causes of Death, the Danish National Prescription Registry, the Attainment Register and the Integrated Database for Labour Market Research to get information on vital status, migration, cancer, hospital contacts, causes of death, dispensed prescriptions, education and employment. Using this design, rates of a range of outcomes have been compared between HIV-infected patients and the comparison cohort, as well as between families of these two cohorts in order to disaggregate the effects of HIV infection and familial/environmental factors. Data can be shared with foreign institutions following approval from the Danish Data Protection Agency. Potential collaborators can contact the study director, Niels Obel (e-mail: niels.obel@regionh.dk).

Late HIV diagnosis is detrimental both to the individual and to society. Strategies to improve early diagnosis of HIV must be a key health care priority. We examined whether nation-wide electronic registry data could be used to predict HIV status using machine learning algorithms. We extracted individual level data from Danish registries and used algorithms to predict HIV status. We used various algorithms to train prediction models and validated these models. We calibrated the models to mimic different clinical scenarios and created confusion matrices based on the calibrated models. A total 4,384,178 individuals, including 4,350 with incident HIV, were included in the analyses. The full model that included all variables that included demographic variables and information on past medical history had the highest area under the receiver operating characteristics curves of 88·4% (95%CI: 87·5% - 89·4%) in the validation dataset. Performance measures did not differ substantially with regards to which machine learning algorithm was used. When we calibrated the models to a specificity of 99·9% (pre-exposure prophylaxis (PrEP) scenario), we found a positive predictive value (PPV) of 8·3% in the full model. When we calibrated the models to a sensitivity of 90% (screening scenario), 384 individuals would have to be tested to find one undiagnosed person with HIV. Machine learning algorithms can learn from electronic registry data and help to predict HIV status with a fairly high level of accuracy. Integration of prediction models into clinical software systems may complement existing strategies such as indicator condition-guided HIV testing and prove useful for identifying individuals suitable for PrEP. The study was supported by funds from the Preben and Anne Simonsens Foundation, the Novo Nordisk Foundation, Rigshospitalet, Copenhagen University, the Danish AIDS Foundation, the Augustinus Foundation and the Danish Health Foundation.