Evolution of recruitment

The Swiss HIV Cohort Study (SHCS) is a large cohort study enrolling patients prospectively since 1988. Some data going back to 1981 have been collected retrospectively. As of December 2016, a total of 19’741 persons have been enrolled in the SHCS. Since 2002, the annual number of newly registered patients is on average around 500 (Figure 1).

The largest proportion of patients were recruited in Swiss University Hospital infectious disease outpatient clinic in Zurich (37.1%). In the 3 other Swiss University Hospital infectious disease outpatient clinics of Lausanne, Geneva and Bern, each contributes about 13-16% of patients, the University Hospital infectious disease outpatient clinic of Basel has 10%. Lugano and St. Gallen, which are two large cantonal hospitals, have 3 and 6%, respectively (Figure 2).


Figure 1: Patients newly registered each year in the Swiss HIV Cohort Study (SHCS), 1984 - 2016

Figure 2: Distribution of patients ever registered in the SHCS by clinical centre (N=19'741)

Of the newly registered patients in 2016, 22.2% were women (Figure 3).

The main three transmission groups IDU (Intravenous Drug User), MSM (Men having Sex with Men) and HET (heterosexual contacts) are well represented. Among patients belonging to the transmission group IDU we further distinguish patients where the most probable cause of infection was intravenous drug use from those where the transmission might have occurred sexually (Figure 4).


Figure 3: Distribution of new patients registered each year in the SHCS by gender, 1986 - 2016

Figure 4: Distribution of patients ever registered in the SHCS by presumed mode of infection, 1986 - 2016

The mean age of patients at the time of registration has increased over the years: for females, it increased from 30 in 1990 to 41 in 2016; for males, it increased from 34 in 1990 to 40 in 2016 (Figure 5).

Figure 6 indicates that the median CD4 cell count at the time of registration, first decreased over time for both sex until 1995, then increased, with some fluctuation, up to nowadays.


Figure 5: Mean age at registration in the SHCS by gender, 1986 - 2016

Figure 6: Mean CD4 cell count at registration in the SHCS by gender, 1986 - 2016

With the advent of combined Antiretroviral Therapy (cART) in 1995-1996 and the hope to eradicate the virus by early treatment, the median CD4 cell count at the initiation of the therapy raised very rapidly. The guidelines for the treatment initiation changed several times which is reflected in our data. Today, early treatment initiation became standard of care and patients are initiating treatment earlier, with higher CD4 cell counts. (Figure 7).

Mortality has substantially decreased since cART became available in 1996 and is still steadily decreasing (Figure 8).


Figure 7: Median CD4 cell count at initiation of cART in treatment naïve patients by presumed mode of infection, in the SHCS by gender, 1996 - 2016

Figure 8: Probability of dying and dropping out in the SHCS, 1991 - 2016

Until end of 2016, 25.0% (4'944) of study participants died, and 5'234 (26.5%) were reported lost from follow-up (drop-outs), because they did not answer, left the country or did not want to participate any more in the study. The number of patients currently followed up in the SHCS is 9’564. This number is steadily increasing since the introduction of cART in 1996. The average follow-up visits per patient in 2016 was 1.8.

The number of patients followed up by other outpatient clinics (e.g. Bienne, Burgdorf, Neuchâtel, etc.) and by private practitioners increased continuously (figure 10). The distribution of private physician is not even. In Geneva, for example, over 57% of participating patients were under the care of private physicians during the year 2016, whereas this figure was less than 20% for Bern (figure 11).


Figure 9: Annual number of patients seen at least once in the SHCS, 1984 - 2016

Figure 10: Annual number of patients visits by type of health care provider in the SHCS, 1987 - 2016

Figure 11: Distribution of visits in the SHCS in 2016, by type of health care provider