The percentage of people presenting with late stage disease at HIV diagnosis varied by country, overall with a range from 28.7% (United States) to 8.8% (Canada), and by transmission categories. The percentage of people diagnosed late was lower in several countries than previously reported (e.g., Canada) 
. The percentage of people diagnosed with AIDS who had their initial HIV diagnosis within 12 months before AIDS diagnosis varied little among countries, except the percentages were somewhat lower in Spain and the United States. Overall, the majority of people diagnosed with HIV were linked to HIV care within 3 months of diagnosis (more than 70%), but varied by age and transmission category. Improvements in detecting HIV earlier and differences in patterns of late presentation at HIV diagnosis among countries may reflect differences in screening practices by providers, public health agencies, and people with HIV.
Screening recommendations, screening patterns independent of screening recommendations, and access to health care influence early detection of HIV infection. Some countries have shifted from HIV testing based on risk assessment to HIV screening in certain settings. For example, in 2006 the U.S. CDC recommended routine HIV screening in clinical settings where HIV prevalence is >0.1 percent and expanded support to state health departments for HIV testing 
. However, the percentage diagnosed late was higher in the United States compared to the other countries included in this analysis. Another factor that can impact access to care is lack of health insurance, with 32% of Latinos, 21% of blacks, and 16% of whites being uninsured in the United States 
. Generally, MSM test more frequently and have lower percentages of late presentation. The higher percentage presenting late for people with infection attributed to heterosexual contact in Australia, France, and Italy may be related to lack of perceived risk or a denial of risk and therefore failure to test for HIV, or a higher percentage of foreign-born people. The higher percentage presenting late among IDU in the United States may be due to not accessing health care due to lack of insurance (United States), social disadvantage, lack of social/familial support, or stigma associated with drug use behaviors. The situation is different in France compared with the United States. Most people who use intravenous drugs in France have been infected with HIV in the 1990s and most have been diagnosed many years ago 
. Very few people who use intravenous drugs were newly diagnosed with HIV, that is less than 100 cases were diagnosed during the analysis year, representing less than 1% of all new HIV cases, and half of these cases were immigrants. Moreover, the second indicator used in this analysis (HIV diagnosis within 12 months before AIDS) shows that only 28% of IDU in France were diagnosed with HIV within 12 months before AIDS diagnosis, a low percentage compared to other categories (70% among heterosexuals, 64% among MSM).
Similar factors may affect linkage to care among IDU (e.g., in Canada and Spain, fewer IDU were linked to care compared with MSM). Effective drug treatment programs may include HIV prevention services, such as HIV testing and linkage to care. Similar to earlier findings from North America 
, in most countries a lower percentages of younger people was linked to care soon after diagnosis compared to older people. Younger people may feel healthy and therefore may not feel the need to engage in care soon after diagnosis. In general, people diagnosed with HIV should receive an initial assessment of immune system status and viral load promptly after diagnosis 
, and with guidelines now recommending treatment be offered to people with less severe disease (e.g., WHO guidelines recommend treatment at CD4 count ≤350 cells/mm3
prompt linkage to care could improve worldwide.
Because not all countries could provide data on stage of disease at diagnosis, we also assessed AIDS diagnosis in relation to the time of HIV diagnosis ( and ). This measure reflects people with AIDS who may have been recently diagnosed or people who were diagnosed with HIV years before their AIDS diagnosis and who may or may not have been on treatment. While this measure is not directly comparable to the late diagnosis measure presented in , and does not reflect people who may have developed AIDS but were promptly treated, it can indicate a need for earlier detection and prompt treatment.
Our analyses are subject to several limitations. Reporting of HIV diagnoses and HIV-related laboratory test results to HIV surveillance differ between countries. For some countries information was not available for the entire population. Classification of severe stage of HIV (i.e., AIDS) may also differ between countries, depending on whether only CD4 test results are considered and/or opportunistic illnesses. We assumed that people who did not have a CD4 count did not have AIDS since if they had severe disease, they would have been diagnosed with AIDS. Our results need to be interpreted in light of the treatment guidelines and health care systems of the respective countries. We measured linkage to care based on CD4 and viral load test results; we did not have information on clinic visits that may not have resulted in such testing. Incomplete reporting of test results may have underestimated linkage to care.
In summary, the percentage with advanced disease at HIV diagnosis and linkage to care vary between the high-income countries included in this analysis. In general, MSM are diagnosed earlier than people with infection attributed to other risk factors. The percentage of people who received assessments of immune status and viral load within 3 months of diagnosis was generally high. Future analyses may need to explore factors within countries that promote higher benchmarks on these indicators and support early diagnosis and prompt linkage to care.