Homozygosity for a missense variant in COMP gene associated with severe pseudoachondroplasia.

The phenotypic spectrum associated with heterozygous mutations in cartilage oligomeric matrix protein gene (COMP) range from a mild form of multiple epiphyseal dysplasia (MED) to pseudoachondroplasia (PSACH). However, the phenotypic effect from biallelic COMP variants is unclear. We investigated a large consanguineous Pakistani family with a severe form of PSACH in 2 individuals. Another 14 family members presented with a mild PSACH phenotype similar to MED. Using exome sequencing and subsequent segregation analysis, we identified homozygosity for a COMP missense variant [c.1423G>A; p.(D475N)] in the 2 severely affected individuals, whereas family members with the mild PSACH phenotype were heterozygous. Our observations show for the first time that a biallelic COMP variant may be associated with pronounced and widespread skeletal malformations suggesting an additive effect of the 2 mutated alleles.

An approach for the identification of exemplar sites for scaling up targeted field observations of benthic biogeochemistry in heterogeneous environments.

Continental shelf sediments are globally important for biogeochemical activity. Quantification of shelf-scale stocks and fluxes of carbon and nutrients requires the extrapolation of observations made at limited points in space and time. The procedure for selecting exemplar sites to form the basis of this up-scaling is discussed in relation to a UK-funded research programme investigating biogeochemistry in shelf seas. A three-step selection process is proposed in which (1) a target area representative of UK shelf sediment heterogeneity is selected, (2) the target area is assessed for spatial heterogeneity in sediment and habitat type, bed and water column structure and hydrodynamic forcing, and (3) study sites are selected within this target area encompassing the range of spatial heterogeneity required to address key scientific questions regarding shelf scale biogeochemistry, and minimise confounding variables. This led to the selection of four sites within the Celtic Sea that are significantly different in terms of their sediment, bed structure, and macrofaunal, meiofaunal and microbial community structures and diversity, but have minimal variations in water depth, tidal and wave magnitudes and directions, temperature and salinity. They form the basis of a research cruise programme of observation, sampling and experimentation encompassing the spring bloom cycle. Typical variation in key biogeochemical, sediment, biological and hydrodynamic parameters over a pre to post bloom period are presented, with a discussion of anthropogenic influences in the region. This methodology ensures the best likelihood of site-specific work being useful for up-scaling activities, increasing our understanding of benthic biogeochemistry at the UK-shelf scale.

Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column.

Shelf sediments underlying temperate and oxic waters of the Celtic Sea (NW European Shelf) were found to have shallow oxygen penetrations depths from late spring to late summer (2.2-5.8 mm below seafloor) with the shallowest during/after the spring-bloom (mid-April to mid-May) when the organic carbon content was highest. Sediment porewater dissolved iron (dFe, <0.15 µm) mainly (>85%) consisted of Fe(II) and gradually increased from 0.4 to 15 µM at the sediment surface to ~100-170 µM at about 6 cm depth. During the late spring this Fe(II) was found to be mainly present as soluble Fe(II) (>85% sFe, <0.02 µm). Sub-surface dFe(II) maxima were enriched in light isotopes (δ56Fe -2.0 to -1.5‰), which is attributed to dissimilatory iron reduction (DIR) during the bacterial decomposition of organic matter. As porewater Fe(II) was oxidised to insoluble Fe(III) in the surface sediment layer, residual Fe(II) was further enriched in light isotopes (down to -3.0‰). Ferrozine-reactive Fe(II) was found in surface porewaters and in overlying core top waters, and was highest in the late spring period. Shipboard experiments showed that depletion of bottom water oxygen in late spring can lead to a substantial release of Fe(II). Reoxygenation of bottom water caused this Fe(II) to be rapidly lost from solution, but residual dFe(II) and dFe(III) remained (12 and 33 nM) after >7 h. Iron(II) oxidation experiments in core top and bottom waters also showed removal from solution but at rates up to 5-times slower than predicted from theoretical reaction kinetics. These data imply the presence of ligands capable of complexing Fe(II) and supressing oxidation. The lower oxidation rate allows more time for the diffusion of Fe(II) from the sediments into the overlying water column. Modelling indicates significant diffusive fluxes of Fe(II) (on the order of 23-31 µmol m-2 day-1) are possible during late spring when oxygen penetration depths are shallow, and pore water Fe(II) concentrations are highest. In the water column this stabilised Fe(II) will gradually be oxidised and become part of the dFe(III) pool. Thus oxic continental shelves can supply dFe to the water column, which is enhanced during a small period of the year after phytoplankton bloom events when organic matter is transferred to the seafloor. This input is based on conservative assumptions for solute exchange (diffusion-reaction), whereas (bio)physical advection and resuspension events are likely to accelerate these solute exchanges in shelf-seas.

Comparing benthic biogeochemistry at a sandy and a muddy site in the Celtic Sea using a model and observations.

Results from a 1D setup of the European Regional Seas Ecosystem Model (ERSEM) biogeochemical model were compared with new observations collected under the UK Shelf Seas Biogeochemistry (SSB) programme to assess model performance and clarify elements of shelf-sea benthic biogeochemistry and carbon cycling. Observations from two contrasting sites (muddy and sandy) in the Celtic Sea in otherwise comparable hydrographic conditions were considered, with the focus on the benthic system. A standard model parameterisation with site-specific light and nutrient adjustments was used, along with modifications to the within-seabed diffusivity to accommodate the modelling of permeable (sandy) sediments. Differences between modelled and observed quantities of organic carbon in the bed were interpreted to suggest that a large part (>90%) of the observed benthic organic carbon is biologically relatively inactive. Evidence on the rate at which this inactive fraction is produced will constitute important information to quantify offshore carbon sequestration. Total oxygen uptake and oxic layer depths were within the range of the measured values. Modelled depth average pore water concentrations of ammonium, phosphate and silicate were typically 5-20% of observed values at the muddy site due to an underestimate of concentrations associated with the deeper sediment layers. Model agreement for these nutrients was better at the sandy site, which had lower pore water concentrations, especially deeper in the sediment. Comparison of pore water nitrate with observations had added uncertainty, as the results from process studies at the sites indicated the dominance of the anammox pathway for nitrogen removal; a pathway that is not included in the model. Macrofaunal biomasses were overestimated, although a model run with increased macrofaunal background mortality rates decreased macrofaunal biomass and improved agreement with observations. The decrease in macrofaunal biomass was compensated by an increase in meiofaunal biomass such that total oxygen demand remained within the observed range. The permeable sediment modification reproduced some of the observed behaviour of oxygen penetration depth at the sandy site. It is suggested that future development in ERSEM benthic modelling should focus on: (1) mixing and degradation rates of benthic organic matter, (2) validation of benthic faunal biomass against large scale spatial datasets, (3) incorporation of anammox in the benthic nitrogen cycle, and (4) further developments to represent permeable sediment processes.

Cenani-Lenz syndrome restricted to limb and kidney anomalies associated with a novel LRP4 missense mutation.

Cenani-Lenz syndrome (CLS) is a rare autosomal recessive developmental disorder of the limbs. The disorder is characterized by complete syndactyly with metacarpal fusions and/or oligodactyly sometimes accompanied by radioulnar synostosis. The clinical expression is variable and kidney agenesis/hypoplasia, craniofacial dysmorphism and teeth abnormalities are frequent features as well as lower limb involvement. CLS was recently associated with mutations in the low-density lipoprotein receptor-related protein 4 (LRP4) gene and dysregulated canonical WNT signaling. We have identified a large consanguineous Pakistani pedigree with 9 members affected by CLS. The affected individuals present with a consistent expression of the syndrome restricted to the limbs and kidneys. Symptoms from the lower limb are mild or absent and there were no radioulnar synostosis or craniofacial involvement. Genetic analysis using autozygosity mapping and sequencing revealed homozygosity for a novel missense mutation c.2858T > C (p.L953P) in the LRP4 gene. The mutation is located in a region encoding the highly conserved low-density lipoprotein receptor repeat class B domain of LRP4. Our findings add to the genotype-phenotype correlations in CLS and support kidney anomalies as a frequent associated feature.

A phosphodiesterase 4 inhibitor, roflumilast N-oxide, inhibits human lung fibroblast functions in vitro.

The PDE4 inhibitor roflumilast mitigates bleomycin-induced lung fibrotic remodeling in rodents. In the current study it was explored whether roflumilast N-oxide, the active metabolite of roflumilast influences functions of cultured lung fibroblasts. Cells of the human foetal lung fibroblast strain GM06114 were stimulated with TNF-alpha (5 ng ml(-1)) and cell surface ICAM-1 and eotaxin release were assessed. [methyl-(3)H] thymidine incorporation was measured following stimulation with bFGF (10 ng ml(-1)). alpha-Smooth muscle actin (protein), CTGF (mRNA) and fibronectin (mRNA) were determined secondary to TGFbeta1 (1 ng ml(-1)). In the presence of PGE(2) (1 nM), roflumilast N-oxide reduced TNF-alpha-induced ICAM-1 and eotaxin by about 70% and >90% with half-maximum inhibition at 0.9 nM and 0.5 nM, respectively. Roflumilast N-oxide also attenuated [methyl-(3)H] thymidine incorporation secondary to bFGF by about 75% with half-maximum inhibition at 0.7 nM when cells were co-incubated with IL-1beta (10 pg ml(-1)). In the presence of this cytokine roflumilast N-oxide (1 microM) diminished TGFbeta1-induced expression of alpha-smooth muscle actin and transcripts of CTGF and fibronectin. In addition, IL-1beta up-regulated PDE4 activity in the lung fibroblasts. Taken together, these findings indicate that roflumilast N-oxide directly targets human lung fibroblasts, which may at least partially explain the efficacy of roflumilast to mitigate a pulmonary fibrotic response in vivo.

Roflumilast inhibits leukocyte-endothelial cell interactions, expression of adhesion molecules and microvascular permeability.

BACKGROUND AND PURPOSE: The present study addressed the effects of the investigational PDE4 inhibitor roflumilast on leukocyte-endothelial cell interactions and endothelial permeability in vivo and in vitro. EXPERIMENTAL APPROACH: In vivo, intravital video-microscopy was used to determine effects of roflumilast p.o. on leukocyte-endothelial cell interactions and microvascular permeability in rat mesenteric venules. In vitro, the effects of roflumilast N-oxide, the active metabolite of roflumilast in humans, and other PDE4 inhibitors on neutrophil adhesion to tumour necrosis factor alpha (TNFalpha)-activated human umbilical vein endothelial cells (HUVEC), E-selectin expression and thrombin-induced endothelial permeability was evaluated. Flow cytometry was used to determine the effect of roflumilast on N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced CD11b upregulation on human neutrophils. KEY RESULTS: In vivo, roflumilast, given 1 h before lipopolysaccharide (LPS), dose-dependently reduced leukocyte-endothelial cell interactions in rat mesenteric postcapillary venules. It also diminished histamine-induced microvascular permeability. Immunohistochemical analyses revealed that roflumilast prevented LPS-induced endothelial P- and E-selectin expression. In vitro, roflumilast N-oxide concentration-dependently suppressed neutrophil adhesion to TNFalpha-activated HUVEC and CD11b expression on fMLP-stimulated neutrophils. It also reduced TNFalpha-induced E-selectin expression on HUVEC, when PDE3 activity was blocked. HUVEC permeability elicited by thrombin was concentration-dependently suppressed by roflumilast N-oxide. While roflumilast N-oxide was as potent as roflumilast at inhibiting stimulated endothelial cell and neutrophil functions, both compounds were significantly more potent than the structurally unrelated PDE4 inhibitors, rolipram or cilomilast. CONCLUSIONS AND IMPLICATIONS: These findings further support earlier observations on the inhibition of inflammatory cell influx and protein extravasation by roflumilast in vivo.

Congenital ichthyosis: mutations in ichthyin are associated with specific structural abnormalities in the granular layer of epidermis.

BACKGROUND: Autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of skin disorders. Several mutant genes have been identified in ARCI, but the association between genotype and phenotype is poorly understood. METHODS: To investigate genotype-phenotype correlations in ARCI, we selected 27 patients from 18 families with specific ultrastructural features of the epidermis. The characteristic findings using electron microscopy (EM) were abnormal lamellar bodies and elongated membranes in the stratum granulosum, classified as ARCI EM type III. DNA samples from a subset of affected individuals were screened for homozygous genomic regions, and a candidate gene region was identified on chromosome 5q33. The region coincides with the ichthyin gene, previously reported as mutated in ARCI. RESULTS: Mutation screening of ichthyin revealed missense or splice-site mutations in affected members from 16 of 18 (89%) families with characteristics of ARCI EM type III. In a control group of 18 patients with ARCI without EM findings consistent with type III, we identified one patient homozygous for a missense mutation in ichthyin. DISCUSSION: Our findings indicate a strong association between ultrastructural abnormalities in the granular layer of epidermis and ichthyin mutations. The results also suggest that EM provides a tool for specific diagnosis in a genetically homogenous subgroup of patients with ARCI.

A founder mutation for ichthyosis prematurity syndrome restricted to 76 kb by haplotype association.

Autosomal recessive congenital ichthyosis (ARCI) is a group of keratinisation disorders that includes the ichthyosis prematurity syndrome (IPS). IPS is rare and almost exclusively present in a restricted region in the middle of Norway and Sweden, which indicates a founder effect for the disorder. We recently reported linkage of IPS to chromosome 9q34, and we present here the subsequent fine-mapping of this region with known and novel microsatellite markers as well as single nucleotide polymorphisms (SNPs). Allelic association, evaluated with Fisher's exact test and P (excess), was used to refine the IPS haplotype to approximately 1.6 Mb. On the basis of the average length of the haplotype in IPS patients, we calculated the age of a founder mutation to approximately 1,900 years. The IPS haplotype contains a core region of 76 kb consisting of four marker alleles shared by 97.7% of the chromosomes associated with IPS. This region spans four known genes, all of which are expressed in mature epidermal cells. We present the results from the analysis of these four genes and their corresponding transcripts in normal and patient-derived samples.

Hospital care of osteoporosis-related vertebral fractures.

Resource implications of hospitalization for osteoporosis-related vertebral fracture are sparsely documented. This study utilized data abstracted from a national sample of hospitalized patients to identify characteristics of patients who are hospitalized with vertebral fracture and their patterns of resource utilization. These were compared with patterns observed for hip fracture hospitalizations. Data from the Nationwide Inpatient Sample (NIS) for 1997 were used to identify men and women age 45 years and above who had a primary diagnosis of vertebral fracture. After patients whose fractures might have been due to metastatic cancer or severe trauma were excluded, 68,901 individuals hospitalized for vertebral fracture were identified. Seventy-seven percent of these were women, most were white, 75 years and older, and had multiple comorbid diagnoses. Total charges averaged 8000-10,000 US dollars per hospitalization and were higher in men. Mean length of stay was just under 6 days and more than 50% of discharged patients required some form of continuing care. Hospitalizations for vertebral fracture occurred at only one-fourth the rate of those for hip fracture, and created only half the hospital charges per admission. Vertebral fracture accounted for over 400,000 total hospital days and generated charges in excess of 500 million US dollars. This resource impact is considerably higher than has been described in prior studies.

Truncating ribosomal protein S19 mutations and variable clinical expression in Diamond-Blackfan anemia.

Diamond-Blackfan anemia (DBA) is a rare constitutional erythroblastopenia characterized by a specific defect in erythroid differentiation. Recently, mutations in the gene encoding ribosomal protein (RP) S19 were found in a subset of patients with the disease. To characterize further RPS19 mutations and to investigate genotype-phenotype relationships, we screened this gene for mutations in patients with DBA by direct sequencing and Southern-blot analysis. Four novel mutations were identified. A G120A nonsense mutation resulting in a stop at codon 33, a C302T nonsense mutation introducing a premature stop at codon 84, and a 327delG which results in a frame shift at codon 103. A fourth and more complex mutation (TT157-158AA, 160insCT) resulting in a Leu45Gln and a frame shift from codon 47 was found in three affected family members with variable phenotypes. The different clinical expression for identical mutations suggest the presence of other modulating factors for the disease. The mutations presented here further support the role of RPS19 in erythropoietic differentiation and proliferation.

The gene encoding ribosomal protein S19 is mutated in Diamond-Blackfan anaemia.

Diamond-Blackfan anaemia (DBA) is a constitutional erythroblastopenia characterized by absent or decreased erythroid precursors. The disease, previously mapped to human chromosome 19q13, is frequently associated with a variety of malformations. To identify the gene involved in DBA, we cloned the chromosome 19q13 breakpoint in a patient with a reciprocal X;19 chromosome translocation. The breakpoint occurred in the gene encoding ribosomal protein S19. Furthermore, we identified mutations in RPS19 in 10 of 40 unrelated DBA patients, including nonsense, frameshift, splice site and missense mutations, as well as two intragenic deletions. These mutations are associated with clinical features that suggest a function for RPS19 in erythropoiesis and embryogenesis.

Multicenter outcome study of cancer patients admitted to the intensive care unit: a probability of mortality model.

PURPOSE: To develop prospectively and validate a model for probability of hospital survival at admission to the intensive care unit (ICU) of patients with malignancy. PATIENTS AND METHODS: This was an inception cohort study in the setting of four ICUs of academic medical centers in the United States. Defined continuous and categorical variables were collected on consecutive patients with cancer admitted to the ICU. A preliminary model was developed from 1,483 patients and then validated on an additional 230 patients. Multiple logistic regression modeling was used to develop the models and subsequently evaluated by goodness-of-fit and receiver operating characteristic (ROC) analysis. The main outcome measure was hospital survival after ICU admission. RESULTS: The observed hospital mortality rate was 42%. Continuous variables used in the ICU admission model are PaO2/FiO2 ratio, platelet count, respiratory rate, systolic blood pressure, and days of hospitalization pre-ICU. Categorical entries include presence of intracranial mass effect, allogeneic bone marrow transplantation, recurrent or progressive cancer, albumin less than 2.5 g/dL, bilirubin > or = 2 mg/dL, Glasgow Coma Score less than 6, prothrombin time greater than 15 seconds, blood urea nitrogen (BUN) greater than 50 mg/dL, intubation, performance status before hospitalization, and cardiopulmonary resuscitation (CPR). The P values for the fit of the preliminary and validation models are .939 and .314, respectively, and the areas under the ROC curves are .812 and .802. CONCLUSION: We report a disease-specific multivariable logistic regression model to estimate the probability of hospital mortality in a cohort of critically ill cancer patients admitted to the ICU. The model consists of 16 unambiguous and readily available variables. This model should move the discussion regarding appropriate use of ICU resources forward. Additional validation in a community hospital setting is warranted.

The Logistic Organ Dysfunction system. A new way to assess organ dysfunction in the intensive care unit. ICU Scoring Group.

OBJECTIVE: To develop an objective method for assessing organ dysfunction among intensive care unit (ICU) patients on the first day of the ICU stay. DESIGN AND SETTING: Physiological variables defined dysfunction in 6 organ systems. Logistic regression techniques were used to determine severity levels and relative weights for the Logistic Organ Dysfunction (LOD) score and for conversion of the LOD score to a probability of mortality. PATIENTS: A total of 13 152 consecutive admission to 137 adult medical/surgical ICUs in 12 countries from the European/North American Study of Severity Systems. OUTCOME MEASURES: Patient vital status at hospital discharge. RESULTS: The LOD System identified from 1 to 3 levels of organ dysfunction for 6 organ systems: neurologic, cardiovascular, renal, pulmonary, hematologic, and hepatic. From 1 to 5 LOD points were assigned to the levels of severity, and the resulting LOD scores ranged from 0 to 22 points. Model calibration was very good in the developmental and validation samples (P=.21 and P=.50, respectively), as was model discrimination (area under the receiver operating characteristic curves of 0.843 and 0.850, respectively). CONCLUSION: The LOD System provides an objective tool for assessing severity levels for organ dysfunction in the ICU, a critical component in the conduct of clinical trials. Neurologic, cardiovascular, and renal dysfunction were the most severe organ dysfunctions, followed by pulmonary and hematologic dysfunction, with hepatic dysfunction the least severe. The LOD System takes into account both the relative severity among organ systems and the degree of severity within an organ system.

Factors affecting the performance of the models in the Mortality Probability Model II system and strategies of customization: a simulation study.

OBJECTIVES: To examine the impact of hospital mortality and intensive care unit (ICU) size on the performance of the Mortality Probability Model II system for use in quality assessment, and to examine the ability of model customization to produce accurate estimates of hospital mortality to characterize patients by severity of illness for clinical trials. DESIGN: Prospective evaluation of model performance, using retrospective data. SETTING: Data for the simulation were assembled from six adult medical and surgical ICUs in Massachusetts and New York. PATIENTS: Consecutive admissions (n = 4,224) to the Massachusetts and New York ICUs were studied. The mortality rate in the database was 18.7%. INTERVENTIONS: A computer simulation of several different hospital mortality rates and ICU sample sizes, using a multicenter database of consecutive ICU admissions, was utilized. We simulated 20 different mortality rates by randomly changing the outcomes at hospital discharge from "survived" to "deceased" and from "deceased" to "survived". Four sample size simulations used 75%, 50%, 25%, and 10% of the database. Ten replications of each mortality rate and samples size were constructed, and model calibration and discrimination were assessed for each replication. Model coefficients were customized, using logistic regression. MEASUREMENTS AND MAIN RESULTS: Vital status at hospital discharge was the outcome measure among the ICU patient population. Model performance was assessed using the Hosmer-Lemeshow C statistic for calibration, and the area under the receiver operating characteristic curve for discrimination. Goodness-of-fit tests and receiver operating characteristic curve areas demonstrated that the models were sensitive to differences in hospital mortality, indicating that they are useful quality assurance tools. Goodness-of-fit tests were more sensitive than the receiver operating characteristic curve areas. The further the hospital mortality rate diverged from the original rate, the worse the performance of the model. Sample size had an impact on these results. The smaller the sample size, the less likely the model was to perform poorly. Model coefficients were successfully customized to demonstrate that improved model performance can be achieved when necessary for clinical trial stratification. CONCLUSION: Mortality Probability Model II models can be used to assess quality of care in ICUs, but the size of the sample should be considered when assessing calibration and discrimination.

Outcome prediction for individual intensive care patients: useful, misused, or abused?

Probabilities of hospital mortality provide meaningful information in many contexts, such as in discussions of patient prognosis by intensive care physicians, in patient stratification for analysis of clinical trial data by researchers, and in hospital reimbursement analysis by insurers. Use of probabilities as binary predictors based on a cut point can be misleading for making treatment decisions for individual patients, however, even when model performance is good overall. Alternative models for estimating severity of illness in intensive care unit (ICU) patients, while demonstrating good agreement for describing patients in the aggregate, are shown to differ considerably for individual patients. This suggests that identifying patients unlikely to benefit from ICU care by using models must be approached with considerable caution.

Customized probability models for early severe sepsis in adult intensive care patients. Intensive Care Unit Scoring Group.

OBJECTIVE: To develop customized versions of the Simplified Acute Physiology Score II (SAPS II) and the 24-hour Mortality Probability Model II (MPM II) to estimate the probability of mortality for intensive care unit patients with early severe sepsis. DESIGN AND SETTING: Logistic regression models developed for patients with severe sepsis in a database of adult medical and surgical intensive care units in 12 countries. PATIENTS: Of 11,458 patients in the intensive care unit for at least 24 hours, 1130 had severe sepsis based on criteria of the American College of Chest Physicians and the Society of Critical Care Medicine (systemic inflammatory response syndrome in response to infection, plus hypotension, hypoperfusion, or multiple organ dysfunction). RESULTS: In patients with severe sepsis, mortality was higher (48.0% vs 19.6% among other patients) and 28-day survival was lower. The customized SAPS II was well calibrated (P = .92 for the goodness-of-fit test) and discriminated well (area under the receiver operating characteristic [ROC] curve, 0.78). Performance in the validation sample was equally good (P = .85 for the goodness-of-fit test; area under the ROC curve, 0.79). The customized MPM II was well calibrated (P = .92 for the goodness-of-fit test) and discriminated well (area under the ROC curve, 0.79). Performance in the validation sample was equally good (P = .52 for the goodness-of-fit test; area under the ROC curve, 0.75). The models are independent of each other; either can be used alone to estimate the probability of mortality of patients with severe sepsis. CONCLUSIONS: Customization provides a simple technique to apply existing models to a subgroup of patients. Accurately assessing the probability of hospital mortality is a useful adjunct for clinical trials.

Mortality probability models for patients in the intensive care unit for 48 or 72 hours: a prospective, multicenter study.

OBJECTIVE: To develop models in the Mortality Probability Model (MPM II) system to estimate the probability of hospital mortality at 48 and 72 hrs in the intensive care unit (ICU), and to test whether the 24-hr Mortality Probability Model (MPM24), developed for use at 24 hrs in the ICU, can be used on a daily basis beyond 24 hrs. DESIGN: A prospective, multicenter study to develop and validate models, using a cohort of consecutive admissions. SETTING: Six adult medical and surgical ICUs in Massachusetts and New York adjusted to reflect 137 ICUs in 12 countries. PATIENTS: Consecutive admissions (n = 6,290) to the Massachusetts/New York ICUs were studied. Of these patients, 3,023 and 2,233 patients remained in the ICU and had complete data at 48 and 72 hrs, respectively. Patients < 18 yrs of age, burn patients, coronary care patients, and cardiac surgical patients were excluded. OUTCOME MEASURE: Vital status at the time of hospital discharge. RESULTS: The models consist of five variables measured at the time of ICU admission and eight variables ascertained at 24-hr intervals. The 24-hr model demonstrated poor calibration and discrimination at 48 and 72 hrs. The newly developed 48- and 72-hr models--MPM48 and MPM72--contain the same 13 variables and coefficients as the MPM24. The models differ only in their constant terms, which increase in a manner that reflects the increasing probability of mortality with increasing length of stay in the ICU. These constant terms were adjusted by a factor determined from the relationship between the data from the six Massachusetts and New York ICUs and a more extensive data set, from which the ICU admission Mortality Probability Model (MPM0) and MPM24 were developed. This latter data set was assembled from ICUs in 12 countries. The MPM48 and MPM72 calibrated and discriminated well, based on goodness-of-fit tests and area under the receiver operating characteristic curve. CONCLUSIONS: Models developed for use among ICU patients at one time period are not transferable without modification to other time periods. The MPM48 and MPM72 calibrated well to their respective time periods, and they are intended for use at specific points in time. The increasing constant terms and associated increase in the probability of hospital mortality exemplify a common clinical adage that if a patient's clinical profile stays the same, he or she is actually getting worse.