gms | German Medical Science

GMS Journal for Medical Education

Gesellschaft für Medizinische Ausbildung (GMA)

ISSN 2366-5017

A single standardized practical training for surgical scrubbing according to EN1500: Effect Quantification, value of the standardized method and comparison with clinical reference groups

research article medicine

  • corresponding author Andreas Fichtner - Universitätsklinikum Halle, Klinik für Anästhesiologie und Operative Intensivmedizin, Leiter Erxleben Lernzentrum, Halle (Saale), Deutschland
  • Elke Haupt - Universitätsklinikum C.-G. Carus, Institut für Hygiene, Dresden, Deutschland
  • Tobias Karwath - TU Dresden, Medizinische Fakultät, Dresden, Deutschland
  • Katharina Wullenk - Ausbildungszentrum für Gesundheitsfachberufe, Halle (Saale), Deutschland
  • Christoph Pöhlmann - Robert-Bosch-Krankenhaus, Abteilung für Labormedizin, Stuttgart, Deutschland
  • Lutz Jatzwauk - Universitätsklinikum C.-G. Carus, Leiter Institut für Hygiene, Dresden, Deutschland

GMS Z Med Ausbild 2013;30(2):Doc24

doi: 10.3205/zma000867, urn:nbn:de:0183-zma0008676

This is the translated version of the article.
The original version can be found at:

Received: May 21, 2012
Revised: February 3, 2013
Accepted: February 8, 2013
Published: May 15, 2013

© 2013 Fichtner et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


The standardized training of practical competences in skills labs is relatively new among German Medical Faculties. The broad acceptance and outstanding evaluation results do not provide objective data on the efficiency and cost-efficiency of these trainings. This study aims on the quantification of the teaching effect of the surgical scrubbing technique EN1500 and its comparison with clinical references of OR personnel.

Methods: 161 4th year medical students were randomized into intervention and control group. The intervention group received a 45 minute standardized peer-teaching training of practical competences necessary in the OR including the scrubbing according to EN1500. Fluorescence dye was mixed in the disinfectant solution. After hand disinfection, standardized fotographs and semi-automated digital processing resulted in quantification of the insufficiently covered hand area. These results were compared with the control group that received the training after the test. In order to provide information on the achieved clinical competence level, the results were compared with the two clinical reference groups.

Results: The intervention group remained with 4,99% (SD 2,34) insufficiently covered hand area after the training compared to the control group 7,33% (SD 3,91), p<0,01. There was no significant difference between control group and reference groups: surgeons 9,32% (SD 4,97), scrub nurses 8,46% (SD 4,66). The student intervention group showed results that were significantly better than the clinical references. The methodic mistake remained negligible. In the sub-group analysis, the students with low or medium experience in surgical scrubbing and hand disinfection derived highest benefit from the training, whereas students with no or high experience did benefit less. All participants showed better results on hand palms compared to back of hand areas.

Discussion: A single standardized peer-teaching of surgical scrubbing and hand disinfection according to EN1500 is sufficient to improve the measurable coverage of hand area and reduce the disinfection gap by 1/3. In absolute measures, the competence level of experienced surgeons and scrub nurses is achieved or even exceeded.

Keywords: Hand Disinfection, Skills Lab, Disinfection Gaps, Standardized Training, Effekt Quantification


With the amendment of the medical licensure act in 2002, a reformation of the curriculum for the study of medicine in Germany took place. The acquisition of clinical practical skills increasingly moved into focus and required the implementation of appropriate learning styles (cf. [1]). Following the examples set by the Netherlands, skills labs were integrated into the student education almost nationwide within a few years (cf. [2]).

According to a survey from the year 2008, 34 out of 36 medical faculties in Germany held skills labs at that time (cf. [3], [4]). After this comprehensive implementation, the question arose as to the efficacy of the training. International studies and above all the consistently very positive evaluations and self-assessments of the students already confirmed the beneficial effects for learners decades ago (cf. [5], [6], [1]).

However, objective and quantitative studies on both the true competence increment of practical skills in such trainings and especially the cost-benefit ratio have been scarcely conducted to date. Using common databases, a literature research on studies relating to the issue of effect quantification of Skills Lab trainings yielded relevant hits only in the single digit range. Even the few published studies often quantified the effect of medical Skills Lab trainings poorly or rather measured effects in the field of theoretical instead of practical competence (cf. [7]). In particular, the categorization and weighting of key items to be recognised as standardized validated check list caused problems which were further amplified by insufficiently precise or standardized measuring tools. Common instruments were non-standardized observation, multiple-choice questions (which are unable to measure practical competence though), and check lists for practical exams (Objective Structured Clinical Examination and Objective Structured Assessment of Technical Skill, respectively) which enable a standardized evaluation of practical skills but are not precise enough to measure small effects (cf. [8], [9])

Especially hygienic skills are easy to learn, but require a high level of precision in daily clinic routine to prevent serious consequences for one or even more patients. Hand disinfection for prevention of infections from even less invasive measures such as vascular accesses is recommended as level of evidence 1A by the Robert Koch Institute. In the light of current clinically relevant challenges in this field, the steady increase of nosocomial infections with multiresistant bacteria requires a standardized education of medical students in all hygienic aspects incorporated in the national catalogue of learning objectives for practical skills (cf. [10]). The complete clinical-practical skills are to be learned and strengthened in view of the latest hygiene guidelines (cf. [11]).

Furthermore, apart from the acquisition of practical skills the verification of the training results represents an important criterion of a Skills Lab training. Besides the correct teaching of the procedure, the question arises regarding the example of hand disinfection as to the influence of standardized processes on the success of the disinfection method (cf. [12]). For this purpose, the identification and precise quantification of disinfection gaps rather than the poorly locatable germ proof shall serve as a measure for the effectiveness of the process since an effective germ reduction is verifiably achieved by sufficient coverage of hand areas (cf. [13]).

Aim of the study

In the setting of a skills lab training, a practical training facility for 4th year medical students shall be established to allow precise quantification of expertise increment and comparison with clinical reference groups (examined OR nurses and surgeons as target reference). Within this scenario the following questions arose:

How can training effects in surgical scrubbing and hand disinfection be measured in a standardized manner? How can the quality of surgical hand disinfection and possible disinfection gaps be precisely quantified?
How well are 4th year medical students able to learn the procedure of surgical hand disinfection after having completed a single standardized practical training (see Figure 1 [Fig. 1])? Are these skills sufficient for a safe application in the daily routine? Are there additional effects of the standardized surgical scrubbing technique in terms of efficient hand disinfection without disinfection gaps?
How good are the skills of the medical students after a single standardized practical training in direct comparison with the reference groups OR personnel and surgeons?

Study design and methods

The pilot study was conducted over a time period of six months at the Medical Faculty of the Technical University Dresden as a prospective, randomized, single blind controlled intervention trial. Approval was obtained by the ethical board of the Technical University Dresden (processing number EK 202082008). As probands, 161 4th year medical students were recruited via online registration and were randomized electronically in an intervention group (IG) and a control group (CG).

For data analysis, the members of both groups were further divided in sub-groups based on their previous practical experience.

As reference groups, 21 examined OR nurses with longtime work experience as well as 16 experienced surgeons from different medical specialist fields were included in the study (see Figure 2 [Fig. 2]).

In all groups, the communicated target value of surgical hand disinfection was the sufficient coverage of all four hand areas for efficient germ reduction (cf. [13]) as well as a threefold disinfection procedure, each with an exposure time of three minutes. The members of all groups were informed that the quality of the hand disinfection procedure was assessed afterwards.

Training course

The student probands and participants of the skills lab training were randomized after informed consent. Subsequently, both the intervention group and the control group were interviewed by means of a questionnaire regarding their previous experience and number of so far performed surgical hand disinfection during OR assistance. Depending on their practical experience, the members of both groups were divided into five sub-groups (0, <10, <50, <100, >100 fold surgical scrubbing and hand disinfection during OR assistance).

The control group disinfected the hands without preceding training with Sterillium? (Bode Chemie Hamburg) mixed with the fluorescent dye Visirub? (Bode Chemie Hamburg) in the manufacturer’s recommended ratio. A complete coverage of all hand areas was supposed to be achieved by the disinfection procedure.

The intervention group received a single standardized practical training in the skills lab. Subsequently, verification of the practical competences in surgical hand disinfection occurred. After the course of the study, the control group was also given the standardized practical training.

The practical training (see Figure 3 [Fig. 3]) was conducted in the peer-teaching technique. A student tutor professionally and didactically trained in the topic carried out training sessions in a strictly standardized form several times per day with small groups consisting of four student participants. After in a survey among students and physicians, correct hand disinfection had been regarded as the most relevant training needs of practical competences, a training program was initiated at the Medical Faculty of the Technical University Dresden. Meanwhile, completing the training program is mandatory for OR admittance at the University Hospital Dresden. The evaluation results for the training program are consistently very good (average grade 1,24 at a scale from 1=very good to 5=fail), and the participants state a big gain in practical competence and safety. The overall cost amounted to approximately EUR 10 per participant.

After evaluation of the raw data, the results of the control group, intervention group, and the five competence adjusted sub-groups were tested for Gaussian distribution. For statistical analysis, t-test for independent samples was performed to compare data between different groups.

Definition of the ideal target value of the training success was realized by gathering disinfection data from clinical reference groups.

Reference group 1 consisted of experienced OR nurses who were instructed during the professional training both by theoretical and practical lessons in the procedure of hygienic and surgical hand disinfection.

Members of the second reference group (2) were recruited out of the students’ potential future occupation group in terms of long-standing surgeons from different medical specialist fields.

The results of the reference groups were also tested for Gaussian distribution.

Measuring technique

The hand disinfectant Sterillium? (Bode Chemie Hamburg) was mixed with the fluorescent dye Visirub? (Bode Chemie Hamburg) in the ratio recommended by the manufacturer. This blend was used for hand disinfection of all test persons. After the predefined disinfection time of three minutes, photos of the air-dried palms and backs of the hands in upright position were taken under an UV lamp with a standardized camera setting. The four taken pictures per proband (two palms and two backs of a proband’s hands) were coded for anonymisation and subsequently analysed by a blinded examiner in a defined operation. For that purpose, an algorithm using the graphics software Microsoft Office Picture Manager©, Origin Lab©, IBM, and SPSS© was specifically developed.

Step 1 of the analysis involved the processing of the five megapixel-sized pictures with the aim to separate the hand’s palm and back areas from the forearm by creating a linear cut at the radial and ulnar angular points. In front of a neutral background, the resulting areas represented the percental amount of disinfectable skin in relation to the overall picture and were expressed as pixel numbers (see Figure 4 [Fig. 4]).

In step 2 of the analysis, the tonal value for a sufficient coverage of the hand with the disinfectant was defined. In every picture, the pixel number of these sufficiently disinfected skin areas was subtracted from the overall pixel number of the disinfectable skin area. Thus, the area remaining after the subtraction process represented the insufficiently covered skin as percentage of the overall hand area (see Figure 5 [Fig. 5]). The pixel number of a tonal value was illustrated by creating a histogram from the original which had been scaled down to a palette of 256 RGB colours (OriginLab©).

In step 3 of the analysis, the created percental results for the insufficiently covered areas of a proband’s four hand surfaces were statistically evaluated.

After the data had been checked for Gaussian distribution, the t-test for independent samples was used as analysing tool for assessing differences of the means.

For quantification of the method error, several raw images underwent ten times each the complete analysing process. The resulting data was also tested for Gaussian distribution.


On study enrollment, the proband distribution was as follows (see Figure 6 [Fig. 6]):

Regarding the key issues of the study, the following results were collected:

1. How can training effects be measured using the example of surgical hand disinfection? How can the quality of surgical hand disinfection and potential disinfection gaps be precisely quantified?

The verification of the method’s overall mistake led to an inherent standard error of +/-0,27% (standard error of the mean). Thus, a method-specific, relevant impact on the measured results could be excluded. Moreover, the presented method for documenting the quality of hand disinfection by a quantitative fluorescence detection approach using a tailored graphical software algorithm has proven its suitability for addressing the following scientific questions.

2. How well can medical students learn depending on their background knowledge the surgical hand disinfection according to EN1500 in a single standardized practical training? Are these skills sufficient for a safe application in the routine? Does the standardized scrubbing technique achieve additional effects in terms of a sufficient hand disinfection without disinfection gaps? (see Figure 7 [Fig. 7])

The single standardized practical training enabled students of the intervention group to produce significantly less disinfection gaps during hand disinfection in comparison to the control group. In addition, the statistical spread of the test results was also reduced in the intervention group.

Weighted according to the previous experiences of the student probands, the sub-group analysis clearly demonstrated better study results for all sub-groups of the intervention group compared to those of the control group (see Figure 8 [Fig. 8]). Strikingly, no significant differences between the intervention and control group could be seen in both the sub-groups with no and high previous experience, respectively. In contrast, the results of the sub-groups with low and medium previous experience were highly significant.

3. How good are the skills of the students after a single standardized practical training in direct comparison to the reference groups OR nurses and surgeons?

In comparison to the reference groups, which represented the clinical standard of the learning objective, the student probands of the intervention group performed significantly better after the single standardized practical training (see Figure 9 [Fig. 9]):

Between the clinical reference groups no significant difference could be observed. However, the OR nurses showed marginally better results on average with slightly less statistical spread.

Of note, the student control group likewise demonstrated better results than both clinical reference groups. When compared to the reference group of surgeons, the threshold of significance was just barely missed.

Further findings

The palms displayed a lower percentage of insufficiently disinfected area than the dorsa of the hands in the control group, intervention group, and in the reference groups, respectively (see Figure 10 [Fig. 10]):


The quite simple practical skill of surgical hand disinfection aims at a complete and even coverage of the hand and should at most feature isolated and very small disinfection gaps. All participants knew about the verification of the disinfection result so that the motivation for the best possible result was apparent in all groups, references groups included.

However, at every hand surface insufficiently covered – albeit minimal – areas could be detected whose fluorescence intensity did not correspond to the expected level after a triple application of the disinfectant according to the procedure of surgical hand disinfection. Due to our specifically developed technique of digital photography and analysis, even these minimal sections could be reliably measured. In this process, the method error was negligibly small.

The standardized, peer-teaching training of the recommended six step scrubbing technique according to EN1500 is suitable to reduce the insufficiently covered hand area by one third. Moreover, it led to a distinctly narrowed statistical spread in the intervention group. These results are even more astonishing as the scrubbing is only a small element of the 45-minute training of practical skills for adequate behaviour in the OR. Similar results in the quality of student- versus physician-instructed training have already been published (cf. [1], [14]).

Surprisingly, the results of the student control group are level with those of the reference groups of surgeons and registered OR nurses with long-standing professional experience. Furthermore, the disinfection results of the student intervention group are significantly better than those of both reference groups. In comparison to the group of surgeons, the OR nurses achieved better results with less statistical spread. This could be explained by the at least semi-standardized practical education of the OR nurses in relation to the academic qualification of the surgeons, especially when considering the effect demonstrated in the intervention group in this study.

All probands had worse outcomes for the dorsa of the hands compared to the palmar areas. However, in relation to all four hand areas the separate analysis of the dorsal and palmar hand areas left the overall statements and their significance level unchanged.

When analysing student results dependent on the competence level of the probands, significant training effects were demonstrated for the sub-groups with low and medium previous experience. In the intervention group, the sub-groups with no and high previous experience, respectively, had only little benefit from the standardized training. Possible explanations could be the low gain in competence by the training in the sub-group with high previous experience (>50 times surgical hand disinfection) and excessive demands by the chosen training level in the sub-group without any previous experience in the OR. Nevertheless, compared to the control group all sub-groups of the intervention group showed better disinfection results as well as a narrowing of the spreading width.

Overall, the training showed a measurable effect and reached or even surpassed the competence level of the clinical references. Considering a reasonable cost-benefit ratio of approximately EUR 10 per student, an optimal training situation for the prospective doctors can be assumed. In this study, visualisation of the disinfection results using a UV lamp strongly contributed to a sustainable sensitisation of the students for the importance of a thorough hygienic and surgical disinfection process to avoid nosocomial infections.

The results clearly demonstrate that such a training is also useful for experienced physicians whom in the context of social learning an important role model is assigned to (cf. [15]).


As a shortcoming it has to be mentionend that the pilot study was conducted with small group sizes. Reference group I comprised a total of 21 qualified OR nurses, whereas in reference group II only 16 surgeons could be included.


Though conceived only as a 45-minute training including further practical contents, the peer-teaching skills lab training of surgical hand disinfection according to EN1500 can be considered an appropriate method for the standardized teaching of medical students in clinical-practical skills. In comparison to the clinical reference, the participants of the intervention group, after a single training session, surpassed examined healthcare professionals with long-standing experience.

Key statements

The presented method of digital allocation of tonal values allows a precise quantification of disinfection gaps during the training of hand disinfection.
A single standardized training of surgical hand disinfection according to EN1500 can be so efficient that the results of the clinical reference groups are outmatched.
The EN1500 technique is suitable to reduce disinfection gaps in surgical hand disinfection.

Competing interests

The authors declare that they have no competing interests.

Bode Chemie Hamburg provided Visirub® free of charge.


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