Retraction speed and chronic poststernotomy pain: A randomized controlled trial

OBJECTIVES

Approximately 30% of patients develop chronic poststernotomy pain (CPSP) following cardiac surgery with sternal retraction. Risk factors have been described but no causal determinants identified. Investigators hypothesized that opening the sternum slowly would impart less force (and thereby less nerve/tissue damage) and translate to a reduced incidence of CPSP. The main objectives were to determine whether or not slower sternal retraction would reduce the incidence of CPSP and improve health-related quality of life.

METHODS

Patients undergoing coronary artery bypass graft surgery were recruited to this randomized controlled trial. Patients were randomized to slow or standard retraction (ie, sternum opened over 15 minutes vs 30 seconds, respectively). Although the anesthesiologist and surgeon were aware of the randomization, the patients, assessors, and postoperative nursing staff remained blinded. Sternotomy pain and analgesics were measured in hospital. At 3, 6, and 12 months postoperatively, all patients completed the Medical Outcomes Survey Short Form and reported on CPSP and complications requiring rehospitalization. Thirty-day rehospitalizations and mortality were recorded.

RESULTS

In total, 326 patients consented to participate and 313 were randomized to slow (n = 159) versus standard retraction (n = 154). No clinically relevant differences were detected in acute pain, analgesic consumption, or the incidence of CPSP or health-related quality of life. Although the slow group had significantly more hospitalizations at 3 and 12 months postoperatively, the reasons were unrelated to retraction speed. No differences were observed in 30-day rehospitalizations or mortality.

CONCLUSIONS

All outcomes were consistent with previous reports, but no clinically significant differences were observed with retraction speed.

Dobutamine and Goal-Directed Fluid Therapy for Improving Tissue Oxygenation in Deep Inferior Epigastric Perforator (DIEP) Flap Breast Reconstruction Surgery: Protocol for a Randomized Controlled Trial

BACKGROUND

Breast reconstruction is an integral part of breast cancer care. There are 2 main types of breast reconstruction: alloplastic (using implants) and autologous (using the patient's own tissue). The latter creates a more natural breast mound and avoids the long-term need for surgical revision-more often associated with implant-based surgery. The deep inferior epigastric perforator (DIEP) flap is considered the gold standard approach in autologous breast reconstruction. However, complications do occur with DIEP flap surgery and can stem from poor flap tissue perfusion/oxygenation. Hence, the development of strategies to enhance flap perfusion (eg, goal-directed perioperative fluid therapy) is essential. Current perioperative fluid therapy is traditionally guided by subjective criteria, which leads to wide variations in clinical practice.

OBJECTIVE

The main objective of this trial is to determine whether the use of minimally invasive cardiac output (CO) monitoring for guiding intravenous fluid administration, combined with low-dose dobutamine infusion (via a treatment algorithm), will increase tissue oxygenation in patients undergoing DIEP flap surgery.

METHODS

With appropriate institutional ethics board and Health Canada approval, patients undergoing DIEP flap surgery are randomly assigned to receive CO monitoring for the guidance of intraoperative fluid therapy in addition to a low-dose dobutamine infusion (which potentially improves flap oxygenation) versus the current standard of care. The primary outcome is tissue oxygenation measured via near-infrared spectroscopy at the perfusion zone furthest from the perforator vessels 45 minutes after vascular reanastomosis of the DIEP flap. Low dose (2.5 μg/kg/hr) dobutamine infusion continues for up to 4 hours postoperatively, provided there are no associated complications (ie, persistent tachycardia). Flap oxygenation, hemodynamic parameters, and any medication-associated side effects/complications are monitored for up to 48 hours postoperatively. Complications, rehospitalizations, and patient satisfaction are also collected until 30 days postoperatively.

RESULTS

Funding and regulatory approvals were obtained in 2019, but the study recruitment was interrupted by the COVID-19 pandemic. As of October 4, 2023, 34 participants have been recruited. Because of the significant delays associated with the pandemic, the expected completion date was extended. We expect the study to be completed and ready for potential news release (as appropriate) and publication by July 2024. No patients have suffered any adverse effects/complications from participating in this study, and none have been lost to follow-up.

CONCLUSIONS

CO-directed fluid therapy in combination with a low-dose dobutamine infusion via a treatment algorithm has the potential to improve DIEP flap tissue oxygenation and reduce complications following DIEP flap breast reconstruction surgery. However, given that the investigators remain blinded to group randomization, no comment can be made regarding the efficacy of this intervention for improving tissue oxygenation at this time. Nevertheless, no patients have been withdrawn for safety concerns thus far, and compliance remains high.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04020172; https://clinicaltrials.gov/study/NCT04020172.

Post-discharge after surgery Virtual Care with Remote Automated Monitoring-1 (PVC-RAM-1) technology versus standard care: randomised controlled trial

OBJECTIVE

To determine if virtual care with remote automated monitoring (RAM) technology versus standard care increases days alive at home among adults discharged after non-elective surgery during the covid-19 pandemic.

DESIGN

Multicentre randomised controlled trial.

SETTING

8 acute care hospitals in Canada.

PARTICIPANTS

905 adults (≥40 years) who resided in areas with mobile phone coverage and were to be discharged from hospital after non-elective surgery were randomised either to virtual care and RAM (n=451) or to standard care (n=454). 903 participants (99.8%) completed the 31 day follow-up.

INTERVENTION

Participants in the experimental group received a tablet computer and RAM technology that measured blood pressure, heart rate, respiratory rate, oxygen saturation, temperature, and body weight. For 30 days the participants took daily biophysical measurements and photographs of their wound and interacted with nurses virtually. Participants in the standard care group received post-hospital discharge management according to the centre's usual care. Patients, healthcare providers, and data collectors were aware of patients' group allocations. Outcome adjudicators were blinded to group allocation.

MAIN OUTCOME MEASURES

The primary outcome was days alive at home during 31 days of follow-up. The 12 secondary outcomes included acute hospital care, detection and correction of drug errors, and pain at 7, 15, and 30 days after randomisation.

RESULTS

All 905 participants (mean age 63.1 years) were analysed in the groups to which they were randomised. Days alive at home during 31 days of follow-up were 29.7 in the virtual care group and 29.5 in the standard care group: relative risk 1.01 (95% confidence interval 0.99 to 1.02); absolute difference 0.2% (95% confidence interval -0.5% to 0.9%). 99 participants (22.0%) in the virtual care group and 124 (27.3%) in the standard care group required acute hospital care: relative risk 0.80 (0.64 to 1.01); absolute difference 5.3% (-0.3% to 10.9%). More participants in the virtual care group than standard care group had a drug error detected (134 (29.7%) v 25 (5.5%); absolute difference 24.2%, 19.5% to 28.9%) and a drug error corrected (absolute difference 24.4%, 19.9% to 28.9%). Fewer participants in the virtual care group than standard care group reported pain at 7, 15, and 30 days after randomisation: absolute differences 13.9% (7.4% to 20.4%), 11.9% (5.1% to 18.7%), and 9.6% (2.9% to 16.3%), respectively. Beneficial effects proved substantially larger in centres with a higher rate of care escalation.

CONCLUSION

Virtual care with RAM shows promise in improving outcomes important to patients and to optimal health system function.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04344665.

Adductor canal block with or without added magnesium sulfate following total knee arthroplasty: a multi-arm randomized controlled trial

PURPOSE

Postoperative analgesia following total knee arthroplasty (TKA) often includes intrathecal opioids, periarticular injection (PAI) of local anesthetic, systemic multimodal analgesia, and/or peripheral nerve blockade. The adductor canal block (ACB) provides analgesia without muscle weakness and magnesium sulphate (MgSO₄) may extend its duration. The purpose of this trial was to compare the duration and quality of early post-TKA analgesia in patients receiving postoperative ACB (± MgSO₄) in addition to standard care.

METHODS

Elective TKA patients were randomized to: 1) sham ACB, 2) ropivacaine ACB, or 3) ropivacaine ACB with added MgSO₄. All received spinal anesthesia with intrathecal morphine, intraoperative PAI, and multimodal systemic analgesia. Patients and assessors remained blinded to allocation. Anesthesiologists knew whether patients had received sham or ACB but were blinded to MgSO_4. The primary outcome was time to first analgesic (via patient-controlled analgesia [PCA] with iv morphine) following ACB. Secondary outcomes were morphine consumption, side effects, visual analogue scale pain scores, satisfaction until 24 hr postoperatively, and length of stay.

RESULTS

Of 130 patients, 121 were included. Nine were excluded post randomization: four were protocol violations, three did not meet inclusion criteria, and two had severe pain requiring open label blockade. There were no differences in the median [interquartile range] time to first PCA request: sham, 310 min [165-550]; ropivacaine ACB, 298 min [120-776]; and ropivacaine ACB with MgSO₄, 270 min [113-780] (P = 0.96). Similarly, we detected no differences in resting pain, opioid consumption, length of stay, or associated side effects until 24 hr postoperatively.

CONCLUSION

We found no analgesic benefit of a postoperative ACB, with or without added MgSO₄, in TKA patients undergoing spinal anesthesia and receiving intrathecal morphine, an intraoperative PAI, and multimodal systemic analgesia.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT02581683); registered 21 October 2015.

Post Discharge after Surgery Virtual Care with Remote Automated Monitoring Technology (PVC-RAM): protocol for a randomized controlled trial

BACKGROUND

After nonelective (i.e., semiurgent, urgent and emergent) surgeries, patients discharged from hospitals are at risk of readmissions, emergency department visits or death. During the coronavirus disease 2019 (COVID-19) pandemic, we are undertaking the Post Discharge after Surgery Virtual Care with Remote Automated Monitoring Technology (PVC-RAM) trial to determine if virtual care with remote automated monitoring (RAM) compared with standard care will increase the number of days adult patients remain alive at home after being discharged following nonelective surgery.

METHODS

We are conducting a randomized controlled trial in which 900 adults who are being discharged after nonelective surgery from 8 Canadian hospitals are randomly assigned to receive virtual care with RAM or standard care. Outcome adjudicators are masked to group allocations. Patients in the experimental group learn how to use the study's tablet computer and RAM technology, which will measure their vital signs. For 30 days, patients take daily biophysical measurements and complete a recovery survey. Patients interact with nurses via the cellular modem-enabled tablet, who escalate care to preassigned and available physicians if RAM measurements exceed predetermined thresholds, patients report symptoms, a medication error is identified or the nurses have concerns they cannot resolve. The primary outcome is number of days alive at home during the 30 days after randomization.

INTERPRETATION

This trial will inform management of patients after discharge following surgery in the COVID-19 pandemic and offer insights for management of patients who undergo nonelective surgery in a nonpandemic setting. Knowledge dissemination will be supported through an online multimedia resource centre, policy briefs, presentations, peer-reviewed journal publications and media engagement.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT04344665.

Atrazine Transport through a Soil-Epikarst System

Row crop and livestock production contaminate soils and groundwater of the karst aquifers within south-central Kentucky's Pennyroyal Plateau. Transport of atrazine from field application to the epikarstic drainage system beneath a field with active row-crop farming was investigated. The Crumps Cave study site is a shallow autogenic drainage system with a recharge area of ∼1 ha that contains two epikarst drains (WF-1 and WF-2) which were monitored for atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA) concentrations from January 2011 to May 2012. Atrazine concentrations in both drains did not increase above winter background levels for nearly 2 mo after application when levels suddenly spiked and reached peak concentrations for the study during an event in May 2011. Atrazine, DEA, and DIA were detected in 100% of samples, and metabolites accounted for 54 to 94% of the monthly total loads, except in May 2011. Median dealkylated metabolite/atrazine ratios (DMAR) were ∼5:1 at both sites, and seasonal DMAR patterns corresponded with changes in soil temperature. These data support the hypothesis that a combination of sorption and degradation in the soil column above the epikarst controlled the transport of atrazine and its metabolites. This resulted in delayed atrazine transport after application and prolonged transport of atrazine and its weakly sorbed metabolites to the epikarst aquifer. Management practices that reduce herbicide inputs, such as diverse crop rotations, cover crops, and use of low-rate and strong-sorbing herbicides, would improve groundwater quality in areas of the Corn Belt with intensive row cropping on karst topography.

Characterization of spaC-type Erysipelothrix sp. isolates causing systemic disease in ornamental fish

Since 2012, low-to-moderate mortality associated with an Erysipelothrix sp. bacterium has been reported in ornamental fish. Histological findings have included facial cellulitis, necrotizing dermatitis and myositis, and disseminated coelomitis with abundant intralesional Gram-positive bacterial colonies. Sixteen Erysipelothrix sp. isolates identified phenotypically as E. rhusiopathiae were recovered from diseased cyprinid and characid fish. Similar clinical and histological changes were also observed in zebrafish, Danio rerio, challenged by intracoelomic injection. The Erysipelothrix sp. isolates from ornamental fish were compared phenotypically and genetically to E. rhusiopathiae and E. tonsillarum isolates recovered from aquatic and terrestrial animals from multiple facilities. Results demonstrated that isolates from diseased fish were largely clonal and divergent from E. rhusiopathiae and E. tonsillarum isolates from normal fish skin, marine mammals and terrestrial animals. All ornamental fish isolates were PCR positive for spaC, with marked genetic divergence (<92% similarity at gyrB, <60% similarity by rep-PCR) between the ornamental fish isolates and other Erysipelothrix spp. isolates. This study supports previous work citing the genetic variability of Erysipelothrix spp. spa types and suggests isolates from diseased ornamental fish may represent a genetically distinct species.

Using a blended e-learning model to provide accessible infection prevention and control training for NHS staff: The NHSU/TVU/Intuition approach

ver the past two decades, healthcare-associated infections (HCAI) have emerged as a significant threat to high quality health care. The technological advances made in the treatment of many diseases and disorders are being undermined by the transmission of infections within healthcare settings, especially the emergence of antimicrobial resistant strains of Staphylococcus aureus and enterococci that are now endemic in some healthcare environments. The financial and personal costs of HCAI in terms of the economic consequences to the National Health Service (NHS) and the physical, social and psychological costs to patients and their relatives have increased both government and public awareness of the risks associated with healthcare interventions and in particular the consequences of HCAI.

The risk of acquiring HCAI continues to attract intense media interest. Reports of dirty hospitals and stories of healthcare workers failing to observe even the most rudimentary hygiene and other infection prevention and control measures are causing profound anxiety among service users. The public is fast losing confidence in the NHS to safely care for them and this dissatisfaction has propelled HCAI to the top of an increasingly urgent political healthcare agenda.

The Department of Health (DH) has focused a number of initiatives on combating HCAI, including the development of national evidence-based infection prevention and control guidelines for acute and primary care settings (Pratt et al, 2001; Pellowe et al, 2003), a research programme to identify a range of effective strategies for combating antimicrobial resistance and more recently setting out a strategy for reducing HCAI and improving environmental hygiene in healthcare settings (DH, 2002; DH, 2004). DH strategy emphasises the importance of ensuring that infection prevention and control training is included in the induction programme for all NHS staff, both clinical and nonclinical, including agency and locum staff, and that this training becomes part of their continuing personal development plans.

Professor Christine Beasley, the chief nursing officer at the DH has since taken responsibility for actualising many aspects of this strategy, especially ensuring that the required training is made available for all 1.3 million NHS staff by the end of 2005. Providing that training became the responsibility of the NHS University (NHSU), which commissioned the Richard Wells Research Centre at Thames Valley University London (TVU) along with their Dublin-based educational development partner, Intuition Publishing Ltd, to develop an appropriate and accessible state-of-the-art blended e-learning training programme.

In this article, we describe how we designed and structured the programme so that it can be used as an essential tool in orientation/induction, staff development and in-service education programmes for all NHS staff.

Are sexual problems more common in women who have had a tubal ligation? A population-based study of Australian women

OBJECTIVE

To investigate whether women who have had a tubal ligation are more likely to experience sexual problems than other women.

DESIGN

Population-based telephone survey.

SETTING

Australia-wide, including cities, regional towns, and rural areas.

POPULATION

A total of 3448 Australian women aged between 16 and 64 years.

METHODS

Women were surveyed using random-digit dialling throughout 2004 and 2005.

MAIN OUTCOME MEASURES

Prevalence of sexual problems and ratings of sexual satisfaction, relationship satisfaction, and sexual pleasure.

RESULTS

From a weighted sample of 2721 women, 447 (16.4%) reported having had a tubal ligation, with 85.0% currently aged between 40 and 64 years. Having a tubal ligation was not associated with any specific sexual problem, such as physical pain during sex or an inability to reach orgasm. In fact, after controlling for age and other sociodemographic differences, sterilised women were significantly less likely than non-sterilised women to lack an interest in having sex (OR 0.69, 95% CI 0.54-0.89), to take 'too long' to reach orgasm (OR 0.69, 95% CI 0.50-0.96), to experience vaginal dryness during sex (OR 0.70, 95% CI 0.50-0.96), and to find sex unpleasurable (OR 0.64, 95% CI 0.46-0.90). Sterilised women were also more likely to experience extremely high levels of sexual satisfaction (OR 1.66, 95% CI 1.27-2.18), relationship satisfaction (OR 1.29, 95% CI 1.01-1.67), and sexual pleasure (OR 1.59, 95% CI 1.20-2.12).

CONCLUSIONS

Our findings suggest no adverse effects, and possibly some benefits, for the sexual lives of women undergoing tubal ligation. These findings should be included with other educational material for couples considering sterilisation as a contraception option.

The potential for CYP2D6 inhibition screening using a novel scintillation proximity assay-based approach

High throughput inhibition screens for human cytochrome P450s (CYPs) are being used in preclinical drug metabolism to support drug discovery programs. The versatility of scintillation proximity assay (SPA) technology has enabled the development of a homogeneous high throughput assay for cytochrome P450 2D6 (CYP2D6) inhibition screen using [O-methyl-(14)C]dextromethorphan as substrate. The basis of the assay was the trapping of the O-demethylation product, [(14)C]HCHO, on SPA beads. Enzyme kinetics parameters V(max) and apparent K(m), determined using pooled human liver microsomes and microsomes from baculovirus cells coexpressing human CYP2D6 and NADPH-cytochrome P450 reductase, were 245 pmol [(14)C]HCHO/min/mg protein and 11 microM, and 27 pmol [(14)C]HCHO/min/pmol and 1.6 microM, respectively. In incubations containing either pooled microsomes or recombinant CYP2D6, [(14)C]dextromethorphan O-demethylase activity was inhibited in the presence of quinidine (IC(50) = 1.0 microM and 20 nM, respectively). By comparison, inhibitors selective for other CYP isoforms were relatively weak (IC(50) > 25 microM). In agreement, a selective CYP2D6 inhibitory monoclonal antibody caused greater than 90% inhibition of [(14)C]dextromethorphan O-demethylase activity in human liver microsomes, whereas CYP2C9/19- and CYP3A4/5-selective antibodies elicited a minimal inhibitory effect. SPA-based [(14)C]dextromethorphan O-demethylase activity was also shown to correlate (r(2) = 0.6) with dextromethorphan O-demethylase measured by high-performance liquid chromatography in a bank of human liver microsomes (N = 15 different organ donors). In a series of known CYP2D6 inhibitors/substrates, the SPA-based assay resolved potent inhibitors (IC(50) < 2 microM) from weak inhibitors (IC(50) >or= 20 microM). It is concluded that the SPA-based assay described herein is suitable for CYP2D6 inhibition screening using either native human liver microsomes or cDNA-expressed CYP2D6.

Response rates of Victorian general practitioners to a mailed survey on miscarriage: randomised trial of a prize and two forms of introduction to the research

AIMS

To identify whether the form of introduction to a study and knowledge of a substantial prize influence the response rate of general practitioners (GPs) to a postal survey.

METHODS

A postal survey of 700 randomly selected Victorian GPs concerning management of early pregnancy bleeding and miscarriage, incorporating two randomised-controlled trials of recruitment methods; analysis of response rates and costs at 4 weeks and 11 weeks.

RESULTS

The response rate was 61.5% of eligible participants. Doctors made aware of a prize were more likely to respond in the first four weeks (difference in response rate 10.2%, 95% confidence interval (CI) 2.8%-17.6%). This difference diminished after the first four weeks. Doctors introduced to the survey by a telephone call were no more likely to respond than those introduced by a postcard. The use of a postcard saved 73% of the cost of introducing the survey by telephone. Female doctors were more likely than males to reply (difference 12.3%, 95% CI 4.7%-19.9%). Rural doctors were no more likely to reply than urban doctors. Very few doctors (16.2%) completed a Practice Assessment activity associated with the survey.

CONCLUSIONS

A valuable prize will accelerate response to a survey by GPs, thereby reducing the costs of follow-up. The cost of telephoned introductions is not justified, when compared with a brief written introduction.

Long-term effects on women of assisted reproduction

The long-term health sequelae for women from assisted reproductive technology (ART) have not been studied extensively. There are a number of reasons that women's health may be compromised after ART procedures, including the consequences of the increased incidence of multiple births, operative deliveries, and preterm infants, the possible adverse effects of the drug regimens used for ovarian stimulation, and the instrumentation involved in ART procedures. In this paper we review the existing literature in these areas. It emphasizes the effects of the drugs used for ovarian stimulation, and in particular the incidence of cancer among women who have undergone ART. The review indicates that there is cause for concern about the long-term effects on women from ART treatments. It highlights the lack of research undertaken in almost all areas related to women's long-term health after ART. In the area of ART and cancer, it draws attention to the lack of conclusive evidence in relation to the posited association between fertility treatments and cancer, resulting from the limited number of very large studies and the need for longer follow-up periods. We make a number of recommendations regarding further research that is needed to address the current shortcomings in the published literature.

PEAPS-Q: a questionnaire to measure the psychosocial effects of having an abnormal pap smear. Psychosocial Effects of Abnormal Pap Smears Questionnaire

We have developed the Psychosocial Effects of Abnormal Pap Smears Questionnaire (PEAPS-Q) which measures distress experienced by women undergoing follow-up investigation after an abnormal Pap smear result. A thorough literature review and qualitative research resulted in the development of a questionnaire which was tested on 350 women attending a Family Planning New South Wales (FPNSW) clinic. This sample included women at different stages of management after detection of a cervical abnormality: 93 first colposcopy clients and 257 follow-up colposcopy clients. Factor analysis identified four dimensions of distress: experience of medical procedures, beliefs/feelings about cervical abnormality and changes in perception of oneself, worry about infectivity and effect on sexual relationships. Repeatability of the PEAPS-Q was indicated by intra-class correlations of 0.88 overall and at least 0.60 for each scale. Internal consistency was shown by Cronbach's alpha of 0.84 overall and at least 0.72 for each scale. Validity was demonstrated by the correlation of scale scores with the 12-item General Health Questionnaire (GHQ) score of 0.32 (95% CI 0.22-0.41). The PEAPS-Q is a valid, reliable and multidimensional instrument for quantifying distress experienced by women with abnormal Pap smears.

Hysterectomy experience among mid-aged Australian women

OBJECTIVES

To determine the rate of oophorectomy in, use of hormone replacement therapy by, and health, social and lifestyle factors of, mid-aged Australian women who have undergone hysterectomy.

DESIGN AND PARTICIPANTS

A community-based cross-sectional survey by telephone interview of a random sample of 2001 Australian-born Melbourne women aged between 45 and 55 years.

MAIN OUTCOME MEASURES

The health status, sociodemographic and lifestyle correlates of women who had undergone hysterectomy compared with women in the natural menopause transition.

RESULTS

Twenty-two per cent of the women had undergone hysterectomy. Of these, 21% had had one ovary removed, and 20% both. Mean age at hysterectomy was 40.4 years. There was no trend in the bilateral oophorectomy rate over the last two decades. Current hormone replacement therapy use increased significantly with surgery, from 17% of non-hysterectomised women to 31% of hysterectomised women, and 49% for women who had undergone hysterectomy and bilateral oophorectomy. Hysterectomised women were significantly more likely to be of lower educational level, and to report a history of troublesome premenstrual complaints, more dilatation and curettage procedures and nongynaecological operations, and use of prescription medications.

CONCLUSIONS

Social and pre-existing health problems influence hysterectomy rates. Many women undergo oophorectomy at hysterectomy despite limited evidence of benefit.

Increasing women's participation in Pap smear screening in Australia--how can we tell if the national policy is effective?

A national policy on the prevention of cervical cancer was launched in 1991. The success of the policy should be judged in terms of the extent that appropriate screening of the 'at risk' population is achieved by the screening program and the degree of reduction of differential screening rates between population groups. The relative cost-effectiveness of the various recruitment strategies chosen to meet the policy's objectives should also be evaluated. A necessary prerequisite for evaluation of the policy is the availability of data about the population screened.