Marcel Zwahlen - Academia.edu (original) (raw)

Papers by Marcel Zwahlen

Research paper thumbnail of Cohort Profile: The Swiss Hepatitis C Cohort Study (SCCS)

International Journal of Epidemiology, 2007

Research paper thumbnail of Evaluating the optimal timing of surgical antimicrobial prophylaxis: study protocol for a randomized controlled trial

Trials, 2014

Background: Surgical site infections are the most common hospital-acquired infections among surgi... more Background: Surgical site infections are the most common hospital-acquired infections among surgical patients. The administration of surgical antimicrobial prophylaxis reduces the risk of surgical site infections. The optimal timing of this procedure is still a matter of debate. While most studies suggest that it should be given as close to the incision time as possible, others conclude that this may be too late for optimal prevention of surgical site infections. A large observational study suggests that surgical antimicrobial prophylaxis should be administered 74 to 30 minutes before surgery. The aim of this article is to report the design and protocol of a randomized controlled trial investigating the optimal timing of surgical antimicrobial prophylaxis. Methods/Design: In this bi-center randomized controlled trial conducted at two tertiary referral centers in Switzerland, we plan to include 5,000 patients undergoing general, oncologic, vascular and orthopedic trauma procedures. Patients are randomized in a 1:1 ratio into two groups: one receiving surgical antimicrobial prophylaxis in the anesthesia room (75 to 30 minutes before incision) and the other receiving surgical antimicrobial prophylaxis in the operating room (less than 30 minutes before incision). We expect a significantly lower rate of surgical site infections with surgical antimicrobial prophylaxis administered more than 30 minutes before the scheduled incision. The primary outcome is the occurrence of surgical site infections during a 30-day follow-up period (one year with an implant in place). When assuming a 5% surgical site infection risk with administration of surgical antimicrobial prophylaxis in the operating room, the planned sample size has an 80% power to detect a relative risk reduction for surgical site infections of 33% when administering surgical antimicrobial prophylaxis in the anesthesia room (with a two-sided type I error of 5%). We expect the study to be completed within three years. Discussion: The results of this randomized controlled trial will have an important impact on current international guidelines for infection control strategies in the hospital. Moreover, the results of this randomized controlled trial are of significant interest for patient safety and healthcare economics. Trial registration: This trial is registered on ClinicalTrials.gov under the identifier NCT01790529.

Research paper thumbnail of Incidence and Correlates of Drug-Eluting Stent Thrombosis in Routine Clinical Practice

Journal of The American College of Cardiology, 2008

We sought to determine the risk of late stent thrombosis (ST) during long-term follow-up beyond 3... more We sought to determine the risk of late stent thrombosis (ST) during long-term follow-up beyond 3 years, searched for predictors, and assessed the impact of ST on overall mortality.

Research paper thumbnail of The Timing of Surgical Antimicrobial Prophylaxis

Annals of Surgery, 2008

Objective: To obtain precise information on the optimal time window for surgical antimicrobial pr... more Objective: To obtain precise information on the optimal time window for surgical antimicrobial prophylaxis. Summary Background Data: Although perioperative antimicrobial prophylaxis is a well-established strategy for reducing the risk of surgical site infections (SSI), the optimal timing for this procedure has yet to be precisely determined. Under today's recommendations, antibiotics may be administered within the final 2 hours before skin incision, ideally as close to incision time as possible. Methods: In this prospective observational cohort study at Basel University Hospital we analyzed the incidence of SSI by the timing of antimicrobial prophylaxis in a consecutive series of 3836 surgical procedures. Surgical wounds and resulting infections were assessed to Centers for Disease Control and Prevention standards. Antimicrobial prophylaxis consisted in single-shot administration of 1.5 g of cefuroxime (plus 500 mg of metronidazole in colorectal surgery). Results: The overall SSI rate was 4.7% (180 of 3836). In 49% of all procedures antimicrobial prophylaxis was administered within the final half hour. Multivariable logistic regression analyses showed a significant increase in the odds of SSI when antimicrobial prophylaxis was administered less than 30 minutes (crude odds ratio ϭ 2.01; adjusted odds ratio ϭ 1.95; 95% confidence interval, 1.4 -2.8; P Ͻ 0.001) and 120 to 60 minutes (crude odds ratio ϭ 1.75; adjusted odds ratio ϭ 1.74; 95% confidence interval, 1.0 -2.9; P ϭ 0.035) as compared with the reference interval of 59 to 30 minutes before incision. Conclusions: When cefuroxime is used as a prophylactic antibiotic, administration 59 to 30 minutes before incision is more effective than administration during the last half hour. (Ann Surg 2008;247: 918 -926) From the

Research paper thumbnail of Comparison of the effectiveness of two mumps vaccines during an outbreak in Switzerland in 1999 and 2000: A case–cohort study

European Journal of Epidemiology, 2003

In two recent nation-wide outbreaks of mumps in Switzerland two-thirds of young children with cli... more In two recent nation-wide outbreaks of mumps in Switzerland two-thirds of young children with clinical mumps had a history of primary vaccination. On average, measles–mumps–rubella (MMR) vaccination coverage is 80%. Two types of vaccine are commonly used: Jeryl-Lynn and Rubini. The effectiveness of the latter has been questioned in several publications. The authors therefore compared Rubini to Jeryl-Lynn in a case–cohort study. The study included 111 young children with clinical mumps who had been reported to the Swiss Federal Office of Public Health (SFOPH) by primary care physicians of the Swiss Sentinel Surveillance Network (SSSN) between January 1999 and May 2000. Sentinel physicians also sampled 661 children from the same birth cohort as the cases. While we found no evidence for the effectiveness of the Rubini strain, vaccination with the Jeryl-Lynn strain was 70% effective against clinical mumps. Furthermore, children vaccinated with the Rubini strain attended primary health care more frequently with clinical mumps than those who had received Jeryl-Lynn (odds ratio: 2.4; 95% confidence interval (CI): 1.3, 4.7). Restricting the analysis to laboratory confirmed cases increased the odds ratio to 18.4 (95% CI: 2.5, 811.2). Our study confirms the low effectiveness of the Rubini strain vaccine in the field. This vaccine should therefore be considered inappropriate for the control and elimination of mumps and its use should be discontinued. As other vaccines with comparable quality and safety standards and a substantially higher effectiveness are available the MMR vaccination program in Switzerland will not be compromised if the use of Rubini is no longer recommended.

Research paper thumbnail of HIV and hepatitis virus infections among injecting drug users in a medically controlled heroin prescription programme

European Journal of Public Health, 2001

Background: In Switzerland, 1,035 patients were accepted for admission to the medically controlle... more Background: In Switzerland, 1,035 patients were accepted for admission to the medically controlled prescription of narcotics programme (PROVE) from 1 January 1994 until 31 December 1996. Heroin, methadone, and morphine were prescribed. This paper presents the prevalence and incidence of HIV and hepatitis B/C infections in the sociomedical context of the participants. Methods: Admission criteria were a minimum age of 20 years, at least a two-year duration of daily heroin consumption, a negative outcome of at least two previous treatments, and documented social and health deficits as a consequence of their heroin dependence. The patients were examined at admission and every six months. A serological test was carried out at the same time for HIV and hepatitis B/C. Results: Serological testing on admission could be performed in more than 80% of the entrants and documented a very high seroprevalence of antibodies against HB CO re (73%) and HCV (82%). The prevalence of HIV and hepatitis B/C increased with duration of drug intake. In the follow-up analysis of seronegative individuals, a halving of the risk of viral hepatitis infection was shown when comparing the first six months with the period greater then six months after PROVE entry. Conclusion: The tests conducted showed high prevalence and incidence rates of HIV and hepatitis B/C among patients who had consumed intravenous drugs for years. The descriptive analysis in heroin-assisted treatment showed a reduction in infection risk for viral hepatitis corresponding to the lower risk behaviour of patients.

Research paper thumbnail of Cohort Profile: The Swiss Hepatitis C Cohort Study (SCCS)

International Journal of Epidemiology, 2007

Research paper thumbnail of Evaluating the optimal timing of surgical antimicrobial prophylaxis: study protocol for a randomized controlled trial

Trials, 2014

Background: Surgical site infections are the most common hospital-acquired infections among surgi... more Background: Surgical site infections are the most common hospital-acquired infections among surgical patients. The administration of surgical antimicrobial prophylaxis reduces the risk of surgical site infections. The optimal timing of this procedure is still a matter of debate. While most studies suggest that it should be given as close to the incision time as possible, others conclude that this may be too late for optimal prevention of surgical site infections. A large observational study suggests that surgical antimicrobial prophylaxis should be administered 74 to 30 minutes before surgery. The aim of this article is to report the design and protocol of a randomized controlled trial investigating the optimal timing of surgical antimicrobial prophylaxis. Methods/Design: In this bi-center randomized controlled trial conducted at two tertiary referral centers in Switzerland, we plan to include 5,000 patients undergoing general, oncologic, vascular and orthopedic trauma procedures. Patients are randomized in a 1:1 ratio into two groups: one receiving surgical antimicrobial prophylaxis in the anesthesia room (75 to 30 minutes before incision) and the other receiving surgical antimicrobial prophylaxis in the operating room (less than 30 minutes before incision). We expect a significantly lower rate of surgical site infections with surgical antimicrobial prophylaxis administered more than 30 minutes before the scheduled incision. The primary outcome is the occurrence of surgical site infections during a 30-day follow-up period (one year with an implant in place). When assuming a 5% surgical site infection risk with administration of surgical antimicrobial prophylaxis in the operating room, the planned sample size has an 80% power to detect a relative risk reduction for surgical site infections of 33% when administering surgical antimicrobial prophylaxis in the anesthesia room (with a two-sided type I error of 5%). We expect the study to be completed within three years. Discussion: The results of this randomized controlled trial will have an important impact on current international guidelines for infection control strategies in the hospital. Moreover, the results of this randomized controlled trial are of significant interest for patient safety and healthcare economics. Trial registration: This trial is registered on ClinicalTrials.gov under the identifier NCT01790529.

Research paper thumbnail of Incidence and Correlates of Drug-Eluting Stent Thrombosis in Routine Clinical Practice

Journal of The American College of Cardiology, 2008

We sought to determine the risk of late stent thrombosis (ST) during long-term follow-up beyond 3... more We sought to determine the risk of late stent thrombosis (ST) during long-term follow-up beyond 3 years, searched for predictors, and assessed the impact of ST on overall mortality.

Research paper thumbnail of The Timing of Surgical Antimicrobial Prophylaxis

Annals of Surgery, 2008

Objective: To obtain precise information on the optimal time window for surgical antimicrobial pr... more Objective: To obtain precise information on the optimal time window for surgical antimicrobial prophylaxis. Summary Background Data: Although perioperative antimicrobial prophylaxis is a well-established strategy for reducing the risk of surgical site infections (SSI), the optimal timing for this procedure has yet to be precisely determined. Under today's recommendations, antibiotics may be administered within the final 2 hours before skin incision, ideally as close to incision time as possible. Methods: In this prospective observational cohort study at Basel University Hospital we analyzed the incidence of SSI by the timing of antimicrobial prophylaxis in a consecutive series of 3836 surgical procedures. Surgical wounds and resulting infections were assessed to Centers for Disease Control and Prevention standards. Antimicrobial prophylaxis consisted in single-shot administration of 1.5 g of cefuroxime (plus 500 mg of metronidazole in colorectal surgery). Results: The overall SSI rate was 4.7% (180 of 3836). In 49% of all procedures antimicrobial prophylaxis was administered within the final half hour. Multivariable logistic regression analyses showed a significant increase in the odds of SSI when antimicrobial prophylaxis was administered less than 30 minutes (crude odds ratio ϭ 2.01; adjusted odds ratio ϭ 1.95; 95% confidence interval, 1.4 -2.8; P Ͻ 0.001) and 120 to 60 minutes (crude odds ratio ϭ 1.75; adjusted odds ratio ϭ 1.74; 95% confidence interval, 1.0 -2.9; P ϭ 0.035) as compared with the reference interval of 59 to 30 minutes before incision. Conclusions: When cefuroxime is used as a prophylactic antibiotic, administration 59 to 30 minutes before incision is more effective than administration during the last half hour. (Ann Surg 2008;247: 918 -926) From the

Research paper thumbnail of Comparison of the effectiveness of two mumps vaccines during an outbreak in Switzerland in 1999 and 2000: A case–cohort study

European Journal of Epidemiology, 2003

In two recent nation-wide outbreaks of mumps in Switzerland two-thirds of young children with cli... more In two recent nation-wide outbreaks of mumps in Switzerland two-thirds of young children with clinical mumps had a history of primary vaccination. On average, measles–mumps–rubella (MMR) vaccination coverage is 80%. Two types of vaccine are commonly used: Jeryl-Lynn and Rubini. The effectiveness of the latter has been questioned in several publications. The authors therefore compared Rubini to Jeryl-Lynn in a case–cohort study. The study included 111 young children with clinical mumps who had been reported to the Swiss Federal Office of Public Health (SFOPH) by primary care physicians of the Swiss Sentinel Surveillance Network (SSSN) between January 1999 and May 2000. Sentinel physicians also sampled 661 children from the same birth cohort as the cases. While we found no evidence for the effectiveness of the Rubini strain, vaccination with the Jeryl-Lynn strain was 70% effective against clinical mumps. Furthermore, children vaccinated with the Rubini strain attended primary health care more frequently with clinical mumps than those who had received Jeryl-Lynn (odds ratio: 2.4; 95% confidence interval (CI): 1.3, 4.7). Restricting the analysis to laboratory confirmed cases increased the odds ratio to 18.4 (95% CI: 2.5, 811.2). Our study confirms the low effectiveness of the Rubini strain vaccine in the field. This vaccine should therefore be considered inappropriate for the control and elimination of mumps and its use should be discontinued. As other vaccines with comparable quality and safety standards and a substantially higher effectiveness are available the MMR vaccination program in Switzerland will not be compromised if the use of Rubini is no longer recommended.

Research paper thumbnail of HIV and hepatitis virus infections among injecting drug users in a medically controlled heroin prescription programme

European Journal of Public Health, 2001

Background: In Switzerland, 1,035 patients were accepted for admission to the medically controlle... more Background: In Switzerland, 1,035 patients were accepted for admission to the medically controlled prescription of narcotics programme (PROVE) from 1 January 1994 until 31 December 1996. Heroin, methadone, and morphine were prescribed. This paper presents the prevalence and incidence of HIV and hepatitis B/C infections in the sociomedical context of the participants. Methods: Admission criteria were a minimum age of 20 years, at least a two-year duration of daily heroin consumption, a negative outcome of at least two previous treatments, and documented social and health deficits as a consequence of their heroin dependence. The patients were examined at admission and every six months. A serological test was carried out at the same time for HIV and hepatitis B/C. Results: Serological testing on admission could be performed in more than 80% of the entrants and documented a very high seroprevalence of antibodies against HB CO re (73%) and HCV (82%). The prevalence of HIV and hepatitis B/C increased with duration of drug intake. In the follow-up analysis of seronegative individuals, a halving of the risk of viral hepatitis infection was shown when comparing the first six months with the period greater then six months after PROVE entry. Conclusion: The tests conducted showed high prevalence and incidence rates of HIV and hepatitis B/C among patients who had consumed intravenous drugs for years. The descriptive analysis in heroin-assisted treatment showed a reduction in infection risk for viral hepatitis corresponding to the lower risk behaviour of patients.