Clinical, biochemical and molecular findings in a series of families with hereditary hyperferritinaemia-cataract syndrome

Hereditary hyperferritinaemia-cataract syndrome (HHCS) is an autosomal dominant disease caused by mutations in the iron responsive element (IRE) of the l-ferritin gene. Despite the elucidation of the genetic basis, the overall clinical spectrum of HHCS has been less well studied as, to date, only individual case reports have been described. Therefore, we studied a total of 62 patients in 14 unrelated families, with nine different mutations. No relevant symptoms other than visual impairment were found to be associated with the syndrome. A marked phenotypic variability was observed, particularly with regard to ocular involvement (i.e. age range at which cataract was diagnosed in 16 subjects with the C39T: 6-40 years). Similarly, serum ferritin levels varied substantially also within subjects sharing the same mutation (i.e. range for the A40G: 700-2412 microg/l). We followed an HHCS newborn in whom well-defined lens opacities were not detectable either at birth or at 1 year. The lens ferritin content was analysed in two subjects who underwent cataract surgery at different ages, with different cataract morphology. Values were similar and about 1500-fold higher than in controls. These observations suggest that: (i) in HHCS the cataract is not necessarily congenital; (ii) in addition to the IRE genotype, other genetic or environmental factors may modulate the phenotype, especially the severity of the cataract.

A human mitochondrial ferritin encoded by an intronless gene

Ferritin is a ubiquitous protein that plays a critical role in regulating intracellular iron homoeostasis by storing iron inside its multimeric shell. It also plays an important role in detoxifying potentially harmful free ferrous iron to the less soluble ferric iron by virtue of the ferroxidase activity of the H subunit. Although excess iron is stored primarily in cytoplasm, most of the metabolically active iron in cells is processed in mitochondria. Little is yet known of how these organelles regulate iron homeostasis and toxicity. Here we report an unusual intronless gene on chromosome 5q23.1 that encodes a 242-amino acid precursor of a ferritin H-like protein. This 30-kDa protein is targeted to mitochondria and processed to a 22-kDa subunit that assembles into typical ferritin shells and has ferroxidase activity. Immunohistochemical analysis showed that it accumulates in high amounts in iron-loaded mitochondria of erythroblasts of subjects with impaired heme synthesis. This new ferritin may play an important role in the regulation of mitochondrial iron homeostasis and heme synthesis.

Personal experience of the treatment of ruptured aortic aneurysms. The prognostic evaluation of some parameters

BACKGROUND

The rupture of an aortic aneurysm is the most frequent and most severe complication, with an incidence of approximately 20-40/100,000 persons each year. The aim of this study was to identify the preoperative, intraoperative and postoperative factors that may influence the mortality rate.

METHODS

Between January 1996 and December 1999 145 patients underwent emergency abdominal aortic repair surgery. One hundred and twenty-three patients represented a ruptured AAA and 22 a fissured aneurysm. One hundred and thirty-one patients were males and 14 were females; their mean age was 75+/-5.06 years. We selected a number of parameters after a review of the international literature and these were analysed in the two classes of survivors. No statistical analyses were performed on fissured aneurysms owing to the scant number of cases examined.

RESULTS

Mortality was 41.4% (44.7% in ruptured aneurysms alone). The following were negative preoperative prognostic factors: old age, hypertension, ASA V, intraoperative anuria and platelet count <100,000. Intraoperative factors included: hypotension, cardiac arrest, onset of anuria, aortic clamping in more than one site, duration of surgery, quantity of RBC and plasma transfused. The main postoperative variables correlated to mortality were: hypotension, hypothermia, onset of anuria, need for further transfusions, high creatinine levels.

CONCLUSIONS

Rapid intervention can minimise mortality in structures with expert teams of surgeons and anesthetists experienced in treating this type of pathology.

Double-gradient denaturing gradient gel electrophoresis assay for identification of L-ferritin iron-responsive element mutations responsible for hereditary hyperferritinemia-cataract syndrome: identification of the new mutation C14G

BACKGROUND

Hereditary hyperferritinemia-cataract syndrome is an autosomic dominant disorder caused by heterogeneous mutations on the iron-responsive element (IRE) of ferritin L-chain mRNA. The mutations described to date were identified by direct sequencing of DNA from probands with hyperferritinemia often associated to bilateral cataracts. A direct genetic approach on a large population is useful to recognize polymorphisms in the DNA region and the prevalence of mutations associated with minor increases in serum ferritin and subclinical cataracts. We developed a rapid DNA scanning technique to detect mutations in a single electrophoretic analysis.

METHODS

The double-gradient denaturing gradient gel electrophoresis (DG-DGGE) method consisted of PCR amplification of the target genomic DNA with GC-clamped oligonucleotides. The sequence encoded the 5' untranslated flanking region of ferritin L-chain mRNA, which includes an IRE stem-loop structure. The product was subjected to DG-DGGE (8.5-15% polyacrylamide and 50-95% denaturant) to separate the homo- and heteroduplexes.

RESULTS

The method clearly identified all eight accessible mutations, including C-G transversions, which are the most difficult to detect. The method was applied to scan DNA samples from 50 healthy subjects and from 230 subjects with serum ferritin >400 microg/L. The new mutation G14C was identified.

CONCLUSIONS

The DG-DGGE method detects all the mutations in the L-ferritin IRE sequence, is rapid and economical, and can be applied to scan large populations. The first population study indicated that the mutations are rare and may involve regions of the IRE structure not yet characterized.

Green fluorescent protein and epitope tag fusion vectors for Dictyostelium discoideum

We have constructed expression vectors for Dictyostelium discoideum which encode a green fluorescent protein (GFP) sequence upstream of a multicloning site for introduction of sequences of interest. Insertion of cDNAs into the multicloning site results in expression of fusion protein bearing an amino- or carboxyl-terminal GFP tag which can be used for fluorescent localization studies in Dictyostelium cells. A parallel construct fuses a FLAG epitope tag at the amino terminus of expressed protein. Each fusion cartridge was placed either in a G418-resistance vector allowing transactivated Ddp2-based extrachromosomal replication or in a vector allowing autonomous Ddp1-based replication. Distinct differences in expression stability were observed in the two vector types. When GFP-expressing cells were analyzed by fluorescence microscopy, significant cell-to-cell variability in expression level was observed when expression was based on the Ddp2 vector, while less cell-to-cell variation in expression level was observed when the Ddp1 backbone was used for expression.

Patients' attitudes towards the use of gloves by healthcare staff

There is a concern among healthcare providers regarding the use of gloves in non-mandated clinical situations and its impact on patient sensitivities. A convenience sample of 76 Israeli hospital inpatients were surveyed to measure patients' attitudes towards the use of gloves by healthcare providers. The Patient Sensitivity Questionnaire (PSQ) was developed and used to collect the data. Overall, patients were found to have a positive attitude towards the use of gloves in most patient care situations. Significant differences in patient attitudes towards glove use were found based on country of origin and number of hospital admissions in the previous year. The study concluded that hospitalized patients, in general, support healthcare providers' use of gloves. In addition, subjects agreed with the (American) Occupational Safety and Health Administration regulations regarding glove use.

Relationship between TNF-alpha and iron metabolism in differentiating human monocytic THP-1 cells

The human monocytic cell line THP-1 differentiates along the macrophage line after phorbol-12-myristate-13-acetate (PMA) supplementation and can be stimulated to secrete tumour necrosis factor alpha (TNF-alpha) by interferon gamma (IFN-gamma) addition. We found that, in the early stage of differentiation (1-48 h), PMA induction elicited an upregulation of intracellular H ferritin and H ferritin binding sites and a downregulation of transferrin receptor. In addition, we found that iron administration to PMA-differentiating cells induced the expression of TNF-alpha mRNA and TNF-alpha secretion to levels even higher than those induced by IFN-gamma alone. The iron chelator desferrioxamine showed the opposite effect and reduced TNF-alpha release. In contrast, preincubation of the cells with iron before PMA induction resulted in a decrease of the TNF-alpha secretion induced by IFN-gamma, whereas the opposite was true after preincubation with desferrioxamine. The data support a co-ordinate interaction between iron and TNF-alpha in monocyte macrophages, with an iron-mediated upregulation of TNF-alpha in the early phase of differentiation and an iron-mediated inhibition at later stages. This complex relationship has to be considered in evaluating the effects of iron on inflammation.

Overexpression of wild type and mutated human ferritin H-chain in HeLa cells: in vivo role of ferritin ferroxidase activity

Transfectant HeLa cells were generated that expressed human ferritin H-chain wild type and an H-chain mutant with inactivated ferroxidase activity under the control of the tetracycline-responsive promoter (Tet-off). The clones accumulated exogenous ferritins up to levels 14-16-fold over background, half of which were as H-chain homopolymers. This had no evident effect in the mutant ferritin clone, whereas it induced an iron-deficient phenotype in the H-ferritin wild type clone, manifested by approximately 5-fold increase of IRPs activity, approximately 2.5-fold increase of transferrin receptor, approximately 1.8-fold increase in iron-transferrin iron uptake, and approximately 50% reduction of labile iron pool. Overexpression of the H-ferritin, but not of the mutant ferritin, strongly reduced cell growth and increased resistance to H(2)O(2) toxicity, effects that were reverted by prolonged incubation in iron-supplemented medium. The results show that in HeLa cells H-ferritin regulates the metabolic iron pool with a mechanism dependent on the functionality of the ferroxidase centers, and this affects, in opposite directions, cellular growth and resistance to oxidative damage. This, and the finding that also in vivo H-chain homopolymers are much less efficient than the H/L heteropolymers in taking up iron, indicate that functional activity of H-ferritin in HeLa cells is that predicted from the in vitro data.

Functional and immunological analysis of recombinant mouse H- and L-ferritins from Escherichia coli

The production and characterization of recombinant mouse H- and L-ferritin chains from Escherichia coli are described. The proteins were efficiently expressed and purified with yields of 7-40 mg per liter of cell culture. They had the expected molecular mass and showed a physical stability analogous to that of the corresponding human ferritins. Mouse H- and L-ferritins had a very similar mobility on denaturing SDS-PAGE, but could be readily separated on nondenaturing PAGE because of the distinct slow mobility of mouse L-ferritin. Direct comparative experiments showed that mouse and human H-ferritins had the same iron incorporation activity, whereas mouse L-ferritin incorporated iron less efficiently than human L-ferritin. The difference was attributed to the substitution of a residue exposed on the cavity surface (Glu140 --> Lys) in mouse L-ferritin, a hypothesis confirmed by the finding that the mouse L-ferritin mutant Lys140-Glu incorporated iron as efficiently as human L-ferritin. Rabbit antisera elicited by the recombinant mouse ferritins were specific for the H- and L-chains and did not cross-react with the human ferritins. The antibodies and the derived specific ELISA assays allow the determination of H- and L-ferritins in mouse tissues.

[Fetal echocardiography volume mode (3 dimensions)]

About 10 out of 100 newborns are affected by congenital heart defects that remain the least easy to detect remain prenatally, despite the relatively high detection rate of fetal malformations. Antenatal diagnosis of congenital heart defects depends on operator experience and skill, but recent techniques of computer assisted ultrasound imaging should be useful by allowing easier recognition of fetal heart anomalies. New imaging procedures include a set of internal fetal views by volume rendering and post acquisition slice selection. Internal views are nearly similar to those obtained during open-heart surgery. In practice, from typical long axis and apical views, two volumes are stored for further examination. Fetal movement, fetal spine and maternal obesity are unfavorable circumstances for useful examination. The routine use of cardiac volume sampling for malformations screening should be possible with increasing speed in image acquisition and in data storage to display real-time 3D imaging.

Immunohistochemistry of HFE in the duodenum of C282Y homozygotes with antisera for recombinant HFE protein

BACKGROUND AND OBJECTIVE

HFE is a class-I MHC related protein which carries the C282Y mutation in most patients with hereditary hemochromatosis, an iron overload disease. HFE protein is expected to have a relevant role in the regulation of duodenal iron absorption, and HFE protein was immunohistochemically identified in the crypt cells. The aim of the work was to analyze whether the C282Y mutation affects HFE accumulation in the duodenum.

DESIGN AND METHODS

We developed antisera for the extracellular portion of recombinant human HFE protein expressed in E. coli. The antisera were specific for HFE protein and the C282Y mutant in immunoblotting, immunoprecipitation and immunocytochemistry experiments of transfected cells, and they did not cross react with HLA antigens in various analyses. The antisera gave positive results in the staining of paraffin-fixed sections of duodenal slices of subjects with hemochromatosis.

RESULTS

The antisera stained evident supranuclear granules in all enterocytes of 7 C282Y homozygous subjects, and a dark area in the same region in 3 other C282Y homozygotes. Granular bodies were absent from the duodenal sections of 8 C282Y negative subjects, from 2 C282Y heterozygotes and 3 C282Y homozygotes, with or without hemochromatosis.

INTERPRETATION AND CONCLUSIONS

The detection of HFE-protein in granular bodies in the enterocytes of the large majority (77%) of C282Y homozygotes and not in other subjects suggests that the mutation facilitates protein accumulation in the duodenum.

A new mutation (G51C) in the iron-responsive element (IRE) of L-ferritin associated with hyperferritinaemia-cataract syndrome decreases the binding affinity of the mutated IRE for iron-regulatory proteins

Hereditary hyperferritinaemia-cataract syndrome is an autosomal dominant disorder characterized by a constitutively increased synthesis of L-ferritin in the absence of iron overload. The disorder is associated with point mutations in the iron-responsive element (IRE) of L-ferritin mRNA. We report a new mutation, G51C, identified in two members of a Canadian family, presenting a moderate increase in serum ferritin and a clinically silent bilateral cataract. Gel retardation assays showed that the binding of the mutated IRE to iron-regulatory proteins (IRPs) was reduced compared with the wild type. Structural modelling predicted that the G51C induces a rearrangement of base pairing at the lateral bulge of the IRE structure which is likely to modify IRE conformation.

Early embryonic lethality of H ferritin gene deletion in mice

Ferritin molecules play an important role in the control of intracellular iron distribution and in the constitution of long term iron stores. In vitro studies on recombinant ferritin subunits have shown that the ferroxidase activity associated with the H subunit is necessary for iron uptake by the ferritin molecule, whereas the L subunit facilitates iron core formation inside the protein shell. However, plant and bacterial ferritins have only a single type of subunit which probably fulfills both functions. To assess the biological significance of the ferroxidase activity associated with the H subunit, we disrupted the H ferritin gene (Fth) in mice by homologous recombination. Fth(+/-) mice are healthy, fertile, and do not differ significantly from their control littermates. However, Fth(-/-) embryos die between 3.5 and 9.5 days of development, suggesting that there is no functional redundancy between the two ferritin subunits and that, in the absence of H subunits, L ferritin homopolymers are not able to maintain iron in a bioavailable and nontoxic form. The pattern of expression of the wild type Fth gene in 9.5-day embryos is suggestive of an important function of the H ferritin gene in the heart.

A single centre's 20 years' experience of columnar-lined (Barrett's) oesophagus diagnosis

BACKGROUND

The pattern of oesophageal carcinoma type has been changing for some time in a number of countries, with adenocarcinoma becoming more frequent

OBJECTIVE

To investigate the prevalence of columnar-lined (Barrett's) oesophagus and oesophageal adenocarcinoma in Barrett's oesophagus during a 20-year period in a single centre.

METHODS

All upper gastrointestinal endoscopy and histology reports for the period January 1977 to December 1996 inclusive were reviewed. Data were analysed from patients who had histologically proven Barrett's oesophagus. The data were analysed as a single cohort and in five-year bands according to the date of diagnosis.

RESULTS

Of 44,721 endoscopies, 636 Barrett's oesophagus cases were diagnosed; 508 (323 males 185 females; M:F ratio 1.7) were histologically proven. The frequency of Barrett's oesophagus detection increased steadily from 0.2% to 1.6% of all endoscopies per five-year band. The M:F ratio and the mean ages at diagnosis (61 years, range 60-63 for males and 69 years, range 68-79 for females) remained constant throughout. Barrett's oesophagus was diagnosed at a younger age in males (peak 60-69 years) compared to females (peak 70-79 years). The male oesophageal adenocarcinoma incidence (11.1%) was almost twice that in females (6.5%). In the majority (81%), the initial diagnosis of oesophageal adenocarcinoma and Barrett's oesophagus was made concurrently.

CONCLUSIONS

The increasing Barrett's oesophagus frequency may reflect an increasing incidence or recognition of this condition or both. Barrett's oesophagus males are more likely to develop oesophageal adenocarcinoma than females.

Overexpression of the hereditary hemochromatosis protein, HFE, in HeLa cells induces and iron-deficient phenotype

A transfectant HeLa cell clone expressing HFE under the control of a tetracycline-repressible promoter was generated. HFE expression was fully repressed by the presence of doxycycline, while it was strongly induced by growth in the absence of doxycycline. HFE accumulation was accompanied by a large (approximately 10-fold) decrease in H- and L-ferritin levels, by a approximately 3-4-fold increase in transferrin receptor, and a approximately 2-fold increase in iron regulatory protein activity. These indices of cellular iron deficiency were reversed by iron supplementation complexes. The overexpressed HFE immunoprecipitated together with transferrin receptor, indicating a physical association which is the likely cause for the observed approximately 30% decrease in 55Fe-transferrin incorporation after 18 h incubation. In the HFE-expressing cells the reduction in transferrin-mediated iron incorporation was partially compensated by a approximately 30% increase in non-transferrin iron incorporation from 55Fe-NTA, evident after prolonged, 18 h, incubations. The findings indicate that HFE binding to transferrin receptor reduces cellular iron availability and regulates the balance between transferrin-mediated and non-transferrin-mediated cellular iron incorporation.

The performance of routine ultrasonographic screening of pregnancies in the Eurofetus Study

OBJECTIVES

The purpose of the Eurofetus Study was to evaluate the accuracy of the antenatal detection of malformations by routine ultrasonographic examination in unselected populations.

STUDY DESIGN

All ultrasonographic diagnoses of malformations and the outcomes of the fetuses were prospectively recorded in 61 European obstetric units over a 3-year period (1990-1993). Also recorded were all cases of malformation diagnosed after abortion or birth for the mothers who underwent follow-up in these centers.

RESULTS

Of 3685 malformed fetuses, 2262 had received diagnoses during pregnancy (sensitivity, 61.4%). Of a total number of 4615 malformations, 2593 were detected (sensitivity, 56.2%). The detection sensitivity was higher for the major than for the minor abnormalities (73.7% vs 45.7%), and the diagnosis was made earlier in the pregnancy (24.2 weeks vs 27.6, P <. 01). Overall, 55% of the major abnormalities were detected within 24 gestational weeks. Within each severity group the accuracy of detection depended on the system. For the major abnormalities it was better for the central nervous system (88.3%) and urinary tract (84. 8%) but lower for the heart and great vessels (38.8%). Detection of minor abnormalities was also effective for the urinary tract (89.1%) but not for the heart and great vessels (20.8%) or the musculoskeletal system (18%). Detection of abnormalities had an influence on the rate of termination of pregnancy. The rate of live births for the mothers bearing fetuses with major abnormalities was lower than that for the mothers in whom no abnormalities were detected, mainly because of the higher rate of elective terminations of pregnancy in the former group.

CONCLUSION

Systematic ultrasonographic screening during pregnancy can now detect a large proportion of fetal malformations, although some still escape detection.

Acute hepatitis C during pregnancy. Case report and review of the literature

Treatment of chronic hepatitis C with interferon is well established (Fried 1995, Zein 1995) though not very successful. We report a case of a pregnant doctor who developed acute hepatitis C six weeks after accidental needle-stick injury from a hepatitis C virus positive patient. We review the literature that deals with such cases.

Incidence of duodenal ulcer healing after 1 week of proton pump inhibitor triple therapy for eradication of Helicobacter pylori. The Lansoprazole Helicobacter Study Group

BACKGROUND

A number of clinical studies have assessed the efficacy of short-term twice-daily Helicobacter pylori eradication regimens but few have investigated the proportion of patients in whom duodenal ulcer disease was healed with these regimens.

AIM

To compare the safety and efficacy of four 1-week H. pylori eradication regimens in the healing of H. pylori associated duodenal ulcer disease.

METHODS

Following endoscopic confirmation of duodenal ulcer disease and a positive CLO test, patients underwent a 13C-urea breath test to confirm H. pylori status. Treatment with one of four regimens: LAC, LAM, LCM or OAM, where L is lansoprazole 30 mg b.d., A is amoxycillin 1 g b.d., M is metronidazole 400 mg b.d., C is clarithromycin 250 mg b.d., and O is omeprazole 20 mg b.d., was assigned randomly to those patients who were H. pylori positive, with 62 (LAC), 64 (LAM), 61 (LCM) and 75 (OAM) patients in each treatment group. Follow-up breath tests and endoscopies were performed at least 28 days after the end of treatment.

RESULTS

Duodenal ulcer disease was healed 28 days after treatment in 53/62 (85.5%) patients who were treated with LAC, 52/64 (81.3%) of patients treated with LAM, 49/61 (80.3%) of patients treated with LCM and 60/75 (80.0%) of patients treated with OAM (intention-to-treat analysis, n = 262, assumed unhealed if no follow-up endoscopy was performed). All the treatments were of similar efficacy (P = 0.85, chi-squared test) with regard to the healing of duodenal ulcer disease.

CONCLUSIONS

The four 1-week treatment regimens were equally effective in healing H. pylori associated duodenal ulcer disease.

Eurofetus: an evaluation of routine ultrasound screening for the detection of fetal defects. Aims and method

The aims of this study are (1) to evaluate the efficiency of ultrasound in detecting CA in low-risk populations of pregnant women by routine screening performed in hospital ultrasound labs (level II); (2) to highlight the areas where improvement could be obtained; (3) to determine efficient timing and number of examinations; (4) to evaluate the psychological returns of detection and nondetection of CA; and (5) to evaluate the cost-effectiveness ratio of antenatal screening of CA. A European collaboration was supposed to help in meeting these objectives because results concerning the analysis of individual CAs or groups of CAs can only be statistically significant when their number is sufficiently large. It was estimated that it was necessary to collect nearly 5,000 CA; this corresponds to about 200,000 pregnant women, the prevalence of malformations at birth being estimated at 2.5%. These conditions yield worthy conclusions, given the following circumstances: a large variety of CA, the extremely low incidence of each CA, the multiple approaches for diagnosis and management, the manifold classes of defects, the differences in gestational age when anomalies are detectable and detected. We study prospectively (1) the reliability of ultrasound in detecting antenatal malformations by recording all CA, ultrasonically suspected and not; (2) the gestational age of anomaly recognition; (3) the response to antenatal diagnosis of CA; (4) the individual outcome of pregnancies; (5) the financial cost of the screening program; and (6) the psychological consequences for the parents.

Sensitivity of routine ultrasound screening of pregnancies in the Eurofetus database. The Eurofetus Team

In this prospective study, we recorded details on 3,685 fetuses with congenital structural abnormalities from an unselected population of women who underwent routine ultrasound examinations during their pregnancies. Overall, 2,262 fetuses were diagnosed as being abnormal before birth (sensitivity = 61.4%). The total number of abnormalities was 4,615, of which 1,733 (37.5%) were major abnormalities. The overall number of detected abnormalities was 2,593 (sensitivity = 56.2%). If only major abnormalities were considered, the sensitivity rose to 73.7%, compared to only 45.7% for the minor abnormalities. Within each severity group, the accuracy of detection varied across systems. For the major abnormalities, it was higher for the central nervous system (88.3%) and urinary tract (84.8%), but lower for heart and great vessels (38.8%). Detection of minor abnormalities was also effective for the urinary tract (89.1%), but not for the heart and great vessels (20.8%) and the musculoskeletal system (18%).

Sensitivity of fetal anomaly detection as a function of time

In this paper, we show that the ratio of the number of fetal anomalies detected by ultrasounds (US) to the total number of cases is not a consistent estimator of the US sensitivity. As Eddy pointed out, when the disease evolves over time, the sensitivity of a test also varies over time according to the development of the disease. To assess correctly the detection capability of a test, it is therefore necessary to estimate a time continuous function (sensitivity function) instead of a single parameter. From a methodological point of view, by considering the "detectability" time of a fetal anomaly as a random variable and parametrizing its distribution function, we estimate the probability that an anomaly is detected conditional upon the precise timing of actually performed US during pregnancy. We fit this model with Eurofetus data (about 7,300 abnormal fetuses), and we compare estimations for different kinds of anomalies (classification based on the system involved and/or severity of the handicap). To allow for heterogeneity of anomalies regarding the detectability time, we generally adopt mixture models. For instance, we select a bi-gamma distribution for major malformations and estimate that 63% of such anomalies are detectable quite early in pregnancy (conditional mean: 15.2 weeks of amenorrhea (WA) +/- 4.2 WA), the others becoming detectable later (30.3 WA +/- 6.4 WA). Such results are then integrated in a cost-effectiveness analysis.