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 2019, a total of 21’029 persons have been enrolled in the SHCS. Since 2002, the annual number of newly registered patients is on average around 500 (fig. 1).


fig. 1: Patients newly registered each year in the Swiss HIV Cohort Study (SHCS), 1984 - 2019

 

The largest proportion of patients were recruited in Swiss University Hospital infectious disease outpatient clinic in Zurich (36.7%). 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 10.7%. Lugano and St. Gallen, which are two large cantonal hospitals, have 3 and 6%, respectively (fig. 2).


fig. 2: Distribution of patients ever registered in the SHCS by clinical centre (N=21’029)

 

Of the newly registered patients in 2019, 18.2% were women (fig. 3).


fig. 3: Distribution of new patients registered each year in the SHCS by gender, 1986 - 2019

 

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 (fig. 4).

 

 

 

 

 

 




fig. 4: Distribution of patients ever registered in the SHCS by presumed mode of infection, 1986 - 2019

 

The mean age of patients at the time of registration has increased over the years: for females, it increased from 30 in 1990 to 40 in 2019; for males, it increased from 34 in 1990 to 41 in 2019 (fig. 5).


fig. 5: Mean age at registration in the SHCS by gender, 1986 - 2019

 

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.


fig. 6: Mean CD4 cell count at registration in the SHCS by gender, 1986 - 2019

 

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 (fig. 7).


fig. 7: Median CD4 cell count at initiation of cART in treatment naïve patients by presumed mode of infection, in the SHCS, 1996 - 2019

 

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

fig. 8: Probability of dying and dropping out in the SHCS, 1991 - 2019

 

Until end of 2019, 24.6% (5’174) of study participants died, and 27.7% (5’833) 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 9’795. This number is steadily increasing since the introduction of cART in 1996. The average follow-up visits per patient in 2019 was 1.8.


fig. 9: Annual number of patients seen at least once in the SHCS, 1984 - 2019

 

The number of patients followed up by other outpatient clinics (e.g. Bienne, Burgdorf, Neuchâtel, etc.) and by private practitioners increased continuously (fig. 10).


fig. 10: Annual number of patients visits by type of health care provider in the SHCS, 1987 - 2019

 

The distribution of private physician is not even. In Geneva, for example, over 59% of participating patients were under the care of private physicians during the year 2019, whereas this figure was only 21% for Bern (figure 11).


fig. 11: Distribution of visits in the SHCS in 2019, by type of health care provider

 

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