Multilevel analysis in health services research: a tutorial

This article describes a well developed, but not yet widespread, statistical method. It presents its distinguishing characteristic (and pre-empts the misunderstanding that all it is about, is including predictors from more than one level). It walks the reader through a simplified example: how can multilevel analysis be used to explain variances in patient satisfaction with the way hospital work is organized. It also discusses the importance of the disciplinary setting for the extra benefit provided by multilevel analysis, as compared to traditional contextual analysis.

[The hospital organization as the staff see it]

BACKGROUND

Reorganisation has become the slogan of how to improve health service without increasing expenses. The question is whether we have the knowledge necessary to build good hospital organisations. The inside information of staff members is one important source for information about hospital organisation.

MATERIAL AND METHODS

The Foundation for Health Services Research performed surveys among doctors, nurses and auxiliaries in Norwegian hospitals in 1998, 2000 and 2001. The questionnaire maps the following dimensions of hospital work: general job satisfaction, workload, leadership, work organisation, professional and personal feedback, competence, continuity, cooperation and architecture. This article presents data from the 2000 study.

RESULTS

About 75% out of 1,832 respondents claim to be satisfied with their jobs, nurses more so than doctors. Small hospitals are experienced as a better place to work than large ones in nearly all respects. Younger employees and staff with a foreign cultural background are less satisfied with their jobs, work organisation and skills. Leadership, professional development as well as personal and professional support seem to be important for job satisfaction in hospitals. Different organisational features motivate doctors and nursing staff.

INTERPRETATION

Hospitals seems to be organised for experienced and Norwegian staff. The actual situation is high personnel turnover with young, inexperienced and mobile health professionals.

Lack of interstitial chromosome 1p deletions in clinically-detected neuroblastoma

Loss of heterozygosity (LOH) of the distal part of the short arm of chromosome 1 in neuroblastoma is a well characterised phenomenon. In addition, previous reports have described interstitial deletions outside the common region of loss on chromosome 1p36, suggesting additional tumour suppressor loci. In this study, we have searched extensively for interstitial 1p deletions in a panel of 67 neuroblastoma samples from clinically-detected cases. We used three VNTR probes and 10 dinucleotide markers from the 1p32-36 regions reported to show interstitial deletions. Fifteen (22%) tumours showed telomeric LOH without evidence for more proximal interstitial deletions. Forty-five tumours showed no LOH or allelic imbalance. Seven (10%) tumours demonstrated allelic imbalance for one or more markers. These tumours were subsequently analysed by fluorescent in situ hybridisation (FISH) and flow cytometry. The patterns found in all seven tumours were consistent with copy number changes of the entire chromosome 1, without evidence for interstitial deletions. This study indicates that interstitial deletions of chromosome 1p are rare in clinically-detected neuroblastoma when analysed by a combination of molecular and cytogenetic techniques.

Cost-effectiveness of periconceptional supplementation of folic acid

BACKGROUND

Supplementation of folic acid prior to and in the beginning of pregnancy may prevent neural tube defects (NTDs) in newborns--such as spina bifida--and possibly other congenital malformations.

OBJECTIVE

To estimate cost effectiveness of periconceptional supplementation of folic acid using pharmaco-economic model calculation.

METHOD

Probabilities for NTDs, risk reductions through periconceptional supplementation of folic acid and lifetime costs of care for children with spina bifida were estimated using Dutch registrations and international literature.

MAIN OUTCOME MEASURE

Cost effectiveness was expressed in net costs per discounted life-year gained. Cost effectiveness was calculated in the baseline and in sensitivity analysis.

RESULTS

Estimated cost effectiveness of periconceptional supplementation of folic acid amounts to NLG 3900 ([symbol: see text] 1800) in the base case. In sensitivity analysis cost effectiveness mostly remains below NLG 10,000 ([symbol: see text] 4500).

CONCLUSION

Periconceptional supplementation of folic acid shows a favorable cost effectiveness. From pharmaco-economic point of view this justifies further stimulation of folic-acid supplementation prior to pregnancy. This can be done through targeted education by health-care workers, such as pharmacists.

A ligand-dependent conformational change of the Na+/galactose cotransporter of Vibrio parahaemolyticus, monitored by tryptophan fluorescence

Purification and reconstitution of the active Vibrio parahaemolyticus Na+/galactose transporter (vSGLT) enables us to do protein chemistry studies on a representative member of this class of membrane transporters. By measuring intrinsic tryptophan (Trp) fluorescence, conformational changes on the binding of substrates could be investigated. Trp fluorescence increased by 6% on the addition of saturating levels of both Na+ and D-galactose, with a K0.5 for D-galactose of 0.6 mM. No change was seen on the addition of Na+ alone or by adding D-galactose in the presence of K+. The Trp fluorescence could be quenched by acrylamide, but not by Cs+or I?. In the presence of Na+ or K+ alone, of Na+ or K+ and D-galactose, of Na+ and L-glucose, or in the absence of ligands, the fluorescence quenches by acrylamide were similar. This indicated that the tryptophan exposure to acrylamide was unchanged in the presence or absence of ligands. No shifts in lem maximum were observed. To find the Trp responsible for the change in fluorescence, Trp 448 in transmembrane helix 11 in the putative sugar-binding pocket was mutated. It was found that W448F showed a similar change in Trp fluorescence upon the addition of D-galactose in the presence of Na+. We conclude that the Trp fluorescence properties of the purified and reconstituted Na+/galactose cotransporter are selectively changed by the transported substrates Na+ and D-galactose, but it is not the Trp (W448) in the sugar translocation pathway that is involved.

Chromosome bands 1p35-36 contain two distinct neuroblastoma tumor suppressor loci, one of which is imprinted

A previous loss of heterozygosity (LOH) study of a series of 91 neuroblastomas suggested that the 1p35-36 region encodes at least two tumor suppressor genes (TSGs) of importance in neuroblastoma development. Here we present the results of a study including 205 neuroblastomas that were analyzed for LOH at chromosome 1 and MYCN amplification. The results corroborate the existence of two TSGs on 1p. Distinct 1p loci seem to be involved in MYCN single copy vs. MYCN amplified neuroblastoma, as these tumors display a different type of shortest region of overlap (SRO). About 15% of MYCN single copy neuroblastomas show 1p deletions of variable length with an SRO of 47 cR at 1p36.3. The lost alleles are preferentially of maternal origin (P = 0.0002), suggesting parental imprinting of the locus. MYCN amplified neuroblastomas have a contrasting pattern of 1p loss. These tumors display much larger deletions of at least 89 cR comprising the region from 1p36.1 to the telomere. LOH of 1p is detected in 86% of the cases. The lost alleles are of random parental origin, suggesting inactivation of a non-imprinted TSG.

Cholate resistance in Lactococcus lactis is mediated by an ATP-dependent multispecific organic anion transporter

The cholate-resistant Lactococcus lactis strain C41-2, derived from wild-type L. lactis MG1363 through selection for growth on cholate-containing medium, displayed a reduced accumulation of cholate due to an enhanced active efflux. However, L. lactis C41-2 was not cross resistant to deoxycholate or cationic drugs, such as ethidium and rhodamine 6G, which are typical substrates of the multidrug transporters LmrP and LmrA in L. lactis MG1363. The cholate efflux activity in L. lactis C41-2 was not affected by the presence of valinomycin plus nigericin, which dissipated the proton motive force. In contrast, cholate efflux in L. lactis C41-2 was inhibited by ortho-vanadate, an inhibitor of P-type ATPases and ATP-binding cassette transporters. Besides ATP-dependent drug extrusion by LmrA, two other ATP-dependent efflux activities have previously been detected in L. lactis, one for the artificial pH probe 2',7'-bis-(2-carboxyethyl)-5(and 6)-carboxyfluorescein (BCECF) and the other for the artificial pH probe N-(fluorescein thio-ureanyl)-glutamate (FTUG). Surprisingly, the efflux rate of BCECF, but not that of FTUG, was significantly enhanced in L. lactis C41-2. Further experiments with L. lactis C41-2 cells and inside out membrane vesicles revealed that cholate and BCECF inhibit the transport of each other. These data demonstrate the role of an ATP-dependent multispecific organic anion transporter in cholate resistance in L. lactis.

Antidepressant drug choice for first users in two regions in The Netherlands

OBJECTIVE

To map the prescribing habits of physicians in two different regions in the Netherlands with respect to antidepressant drug choice for first users.

DESIGN

Retrospective follow-up study.

METHODS

All persons who received an antidepressant drug for the first time during October 1994 to September 1995 were identified from 29 community pharmacies situated in two regions in the Netherlands. Age, gender, type of prescriber, region and the concomitant use of certain groups of drugs as marker for certain diseases were evaluated as determinants for prescribing either a "classic" or a "second generation" antidepressant drug to first users using logistic regression analysis.

RESULTS

We identified 4,637 first users during the study period corresponding with an overall incidence density of 16 per 1,000 person-years. For the majority of first users of both regions, the same five antidepressants were prescribed. However, the two regions differed markedly with regard to the frequency of prescription of the individual antidepressants. Region of living was identified as the most important determinant of prescribing a certain category of antidepressant drugs to first users (OR 2.9 [95% CI 2.5-3.3]). Just a few patient characteristics were associated with antidepressant drug choice. The elderly were more likely to receive a classic antidepressant, as were patients concomitantly using anti-epileptics (OR 0.4 [95% CI 0.3-0.6]). Patients concomitantly using cardiac glycosides were more likely to receive a second generation antidepressant (OR 1.8 [95% CI 1.2-2.1]). With respect to age and the other patient characteristics studied, the same pattern was observed in both regions.

CONCLUSION

Regional differences contributed more to differences in prescribing habits than individual patient characteristics. In order to improve pharmacotherapy with antidepressant drugs relevant patient characteristics should more be taken into account.

Limb mammary syndrome: a new genetic disorder with mammary hypoplasia, ectrodactyly, and other Hand/Foot anomalies maps to human chromosome 3q27

We report on a large Dutch family with a syndrome characterized by severe hand and/or foot anomalies, and hypoplasia/aplasia of the mammary gland and nipple. Less frequent findings include lacrimal-duct atresia, nail dysplasia, hypohydrosis, hypodontia, and cleft palate with or without bifid uvula. This combination of symptoms has not been reported previously, although there is overlap with the ulnar mammary syndrome (UMS) and with ectrodactyly, ectodermal dysplasia, and clefting syndrome. Allelism with UMS and other related syndromes was excluded by linkage studies with markers from the relevant chromosomal regions. A genomewide screening with polymorphic markers allowed the localization of the genetic defect to the subtelomeric region of chromosome 3q. Haplotype analysis reduced the critical region to a 3-cM interval of chromosome 3q27. This chromosomal segment has not been implicated previously in disorders with defective development of limbs and/or mammary tissue. Therefore, we propose to call this apparently new disorder "limb mammary syndrome" (LMS). The SOX2 gene at 3q27 might be considered an excellent candidate gene for LMS because the corresponding protein stimulates expression of FGF4, an important signaling molecule during limb outgrowth and development. However, no mutations were found in the SOX2 open reading frame, thus excluding its involvement in LMS.

Comparison of three assay procedures for gentamicin determination

We examined 50 serum samples, submitted to our laboratory for gentamicin levels, by the enzyme multiplied immuno technique (EMIT), by a radioimmunoassay procedure and by a latex agglutination method. Significant differences in concentrations, rates of throughput, and costs between the latex agglutination and the other two procedures were observed. The precision of the assay ranged from 5.21 to 15.70%, whereas recovery values ranged from 83.8 to 110.0%. The latex agglutination procedure provided simplicity and speed at a relatively low cost. However, the significant analytical difference between this and the other two procedures indicates that the latex agglutination procedure is not adequate for measuring accurate gentamicin levels.