Measuring clinical performance using routinely collected clinical data.

Following the well-publicized problems with paediatric cardiac surgery at the Bristol Royal Infirmary, there is wide public interest in measures of hospital performance. The Kennedy report on the BRI events suggested that such measures should be meaningful to the public, case-mix-adjusted, and based on data collected as part of routine clinical care. We have found that it is possible to predict in-hospital mortality (a measure readily understood by the public) using simple routine data-age, mode of admission, sex, and routine blood test results. The clinical data items can be obtained at a single venesection, are commonly collected in the routine care of patients, are already stored on hospital core IT systems, and so place no extra burden on the clinical staff providing care. Such risk models could provide a metric for use in evidence-based clinical performance management. National application is logistically feasible.

The use of routine laboratory data to predict in-hospital death in medical admissions.

The ability to predict clinical outcomes in the early phase of a patient's hospital admission could facilitate the optimal use of resources, might allow focused surveillance of high-risk patients and might permit early therapy. We investigated the hypothesis that the risk of in-hospital death of general medical patients can be modelled using a small number of commonly used laboratory and administrative items available within the first few hours of hospital admission. Matched administrative and laboratory data from 9497 adult hospital discharges, with a hospital discharge specialty of general medicine, were divided into two subsets. The dataset was split into a single development set, Q(1) (n=2257), and three validation sets, Q(2), Q(3) and Q(4) (n(1)=2335, n(2)=2361, n(3)=2544). Hospital outcome (survival/non-survival) was obtained for all discharges. An outcome model was constructed from binary logistic regression of the development set data. The goodness-of-fit of the model for the validation sets was tested using receiver-operating characteristics curves (c-index) and Hosmer-Lemeshow statistics. Application of the model to the validation sets produced c-indices of 0.779 (Q(2)), 0.764 (Q(3)) and 0.757 (Q(4)), respectively, indicating good discrimination. Hosmer-Lemeshow analysis gave chi(2)=9.43 (Q(2)), chi(2)=7.39 (Q(3)) and chi(2)=8.00 (Q(4)) (p-values of 0.307, 0.495 and 0.433) for 8 degrees of freedom, indicating good calibration. The finding that the risk of hospital death can be predicted with routinely available data very early on after hospital admission has several potential uses. It raises the possibility that the surveillance and treatment of patients might be categorised by risk assessment means. Such a system might also be used to assess clinical performance, to evaluate the benefits of introducing acute care interventions or to investigate differences between acute care systems.

Comparison of P-POSSUM risk-adjusted mortality rates after surgery between patients in the USA and the UK.

BACKGROUND: The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) criteria have been used to assess surgical risk in patients in the UK. The aim was to determine how applicable these criteria are to patients undergoing surgery in the USA. METHODS: Two cohorts of patients undergoing major non-cardiac surgery were followed prospectively in the USA (n = 1056) and the UK (n = 1539). Each patient was assigned a risk score for preoperative physiological status and operative severity using the established POSSUM criteria. Death in hospital was the primary outcome measure. For each patient a predicted risk of death was calculated from Portsmouth POSSUM (P-POSSUM) methodology using an established equation. The relationships between predicted and observed mortality rates in each cohort were investigated by means of multivariate logistic regression. RESULTS: Within each cohort, an increase in risk estimated by P-POSSUM predicted an increase in observed mortality rate (P < 0.001). For any given risk level, however, mortality rates were significantly higher in the UK cohort than in the US cohort (odds ratio 4.50 (95 per cent confidence interval 2.81 to 7.19); Z = 6.25, P < 0.001). CONCLUSION: An increase in predicted risk, based on the P-POSSUM methodology, was associated with a higher mortality rate in patients from both countries. However, risk-adjusted mortality rates following major surgery were four times higher in the UK cohort. These marked differences warrant validation in a larger number of centres.

Towards a national clinical minimum data set for general surgery.

BACKGROUND: Measurement and comparison of surgical performance is accepted as necessary and inevitable. Risk-stratified (case-mix adjusted) models of clinical outcomes form a metric with which to assess performance, but require accurate data. Collecting such data in the clinical environment is time consuming and difficult. This study aimed to construct effective models, for operative and non-operative admissions, from routine clinical data residing in hospital computers, so minimizing data collection and quality problems, and facilitating national implementation. METHODS: Data for 3181 non-operative emergency, 5039 elective and 3043 emergency operative admissions for the 2 years beginning 1 August 1997 were used to generate logistic regression equations for risk of death, which were applied prospectively to the following 3 years' data. RESULTS: The models use urea, haemoglobin, white blood cell count, sodium, potassium, age on admission, sex, British United Provident Association (BUPA) Operative Severity Score (for operative admissions) and, implicitly, mode of admission and mortality at discharge. All three models successfully stratified risk into five or more bands. CONCLUSION: Effective models of mortality, applicable to all general surgical admissions, can be constructed from existing routine clinical data, largely obtained from a single venesection. The data set is a candidate national clinical minimum data set.

Heterogeneity of chemosensitivity of metastatic cutaneous melanoma.

Advanced melanoma has a poor prognosis and chemotherapy provides little benefit for most patients. This may be related to heterogeneity of chemosensitivity as well as frequent constitutive resistance to individual cytotoxic drugs. We have therefore examined the heterogeneity of chemosensitivity in metastatic cutaneous melanoma specimens using an ex vivo ATP-based chemosensitivity assay (ATP-TCA). Melanoma deposits (n=55) in skin or lymph node were tested using the ATP-TCA, performed in three separate laboratories. Analysis of the data collected (based on an arbitrary sensitivity index < 300) shows considerable heterogeneity of chemosensitivity. The most active single cytotoxic agents in the assay were identified as cisplatin, treosulfan, paclitaxel, vinblastine, gemcitabine and mitoxantrone. There was also a limited direct inhibition of melanoma cell growth by interferon-alpha2b, although this agent is known to have a number of indirect biological antitumor effects. Exposure of tumor cells to combinations of drugs at the concentrations tested as single agents showed the most active combinations to be treosulfan+gemcitabine, cisplatin+paclitaxel and vinblastine+paclitaxel. There was considerable heterogeneity of chemosensitivity: some tumors responded well to one agent or combination, while others showed no response to this and instead responded to one of the alternatives tested. Occasional highly resistant tumors showed no response to any of the single agents or combinations tested. The degree of heterogeneity observed suggests that the ATP-TCA could be used to select patients who might benefit from specific chemotherapeutic agents alone or in combination. This provides the rationale for future randomized controlled trials of ATP-TCA-directed chemotherapy versus physician's choice to determine whether assay-directed chemotherapy can improve patient response and survival.

POSSUM and Portsmouth POSSUM for predicting mortality. Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity.

BACKGROUND: There is a need for an accurate measure of surgical outcomes so that hospitals and surgeons can be compared properly regardless of case mix. POSSUM (Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity) uses a physiological score and an operative severity score to calculate risks of mortality and morbidity. In a previous small study it was found that Portsmouth POSSUM (P-POSSUM; a modification of the POSSUM system) provided a more accurate prediction of mortality. METHODS: Some 10000 general surgical interventions (excluding paediatric and day cases) were studied prospectively between August 1993 and November 1995. The POSSUM mortality equation was applied to the full 10000 surgical episodes. The 10000 patients were arranged in chronological order and the first 2500 were used as a training set to produce the modified P-POSSUM predictor equation. This was then applied prospectively to the remaining 7500 patients arranged chronologically in five groups of 1500. RESULTS: The original POSSUM logistic regression equation for mortality overpredicts the overall risk of death by more than twofold and the risk of death for patients at lowest risk (5 per cent or less) by more than sevenfold. The P-POSSUM equation produced a very close fit with the observed in-hospital mortality. CONCLUSION: P-POSSUM provides an accurate method for comparative surgical audit.

An evaluation of the POSSUM surgical scoring system.

POSSUM (Physiological and Operative Severity Score for the enUmeration of Morbidity and mortality) has been studied as a possible surgical audit system for a 9-month interval using a sample of 28 per cent of the general surgical workload. Mortality or survival was analysed as an endpoint. In this sample the published POSSUM predictor equation for mortality overpredicted deaths by a factor of more than two. The bulk of the overprediction occurred in the group at lowest risk (predicted mortality 10 per cent or less), in which death was overpredicted by a factor of six. This is the most important group for audit purposes since it contains the majority of surgical patients and is composed of fit patients undergoing minor surgery. The published predictor equation for mortality returns a minimum predicted mortality of 1.08 per cent, clearly far higher than that expected for a fit patient having minor surgery. Logistic regression was done on a set of 1485 surgical episodes to generate a local predictor equation for mortality. This process gave a predictor equation that fitted well with the observed mortality rate and gave a minimum predicted risk of mortality of 0.20 per cent. The previously published POSSUM predictor equation for mortality performed badly when tested using a standard test of goodness of fit for logistic regression and must be modified.

Transdermal glyceryl trinitrate to allow peripheral total parenteral nutrition: a double-blind placebo controlled feasibility study.

Seventy-two consecutive patients requiring total parenteral nutrition (TPN) were randomized to two groups. Group A received daily a peripheral intravenous regimen which provided 10 g nitrogen and 1400 non-nitrogen kcal (5.9 MJ). Group B received daily a peripheral intravenous regimen which delivered 9.4 g nitrogen and 1900 non-nitrogen kcal (8.0 MJ). Each group was further randomized to receive a self-adhesive patch of transdermal glyceryl trinitrate (GTN) or an identical placebo. Infusion survival was the main end-point. For group A, the median time of infusion survival was 74 h (range: 58-100) in the control group compared with 108 h (range: 68-156) in the group that received transdermal GTN (P less than 0.001). For group B, the median infusion survival was 67 h (range: 46-92) in the control group compared with 103 h (range: 66-151) in the treatment group (P less than 0.001). TPN is feasible via peripheral veins and the incidence of infusion failure can be effectively reduced by transdermal GTN.

Proliferation characteristics of human colorectal carcinomas measured in vivo.

The cell proliferation kinetics of 100 human colonic and rectal adenocarcinomas have been studied in vivo by bromodeoxyuridine infusion and multiparameter flow cytometry. A total of 97 patients, three with synchronous tumours, consented to receive a single bolus dose of 250 mg between 2.4 and 16 h before curative or palliative surgery. By this method, the ploidy pattern, the total and aneuploid labelling indices (LI), the S phase duration (Ts) and the potential doubling time (Tpot) can be estimated. Of the tumours 48 were diploid and 52 were aneuploid. The mean and median total LI of 100 tumours were 9.0 per cent (range 0.7-22.2 per cent). The mean aneuploid LI was 12.1 per cent (median 12.0 per cent, range 2.0-25.5 per cent), and was significantly higher than the total LI (P = 0.01). The labelling index alone is not a sufficient indicator of proliferation, because the Ts also varies within and between tumours. The intertumour range of the Ts varied from 4.0 to 28.6 h. The mean was 14.1 h and the median was 13.1 h. The mean Tpot was 5.9 days (median 3.9 days) with a range of 1.7-21.4 days. No correlation was found between any kinetic parameters and the Dukes' classification or histological classification. The correlation between proliferation and prognosis will be established in due course.

Effect of transdermal glyceryl trinitrate on the survival of peripheral intravenous infusions: a double-blind prospective clinical study.

Phlebitis is the commonest complication of intravenous infusion. It has been suggested that it is initiated by venoconstriction at the infusion site, hence treatment with a vasodilator may reduce its incidence. We carried out a prospective double-blind controlled study of the effect of transdermal glyceryl trinitrate on the survival of peripheral intravenous infusions in 340 patients. Fifty-five per cent (94 out of 170) of the infusions failed in the control group compared with 19 per cent (33 out of 170) in the treatment group (chi 2 = 45, P less than 0.0005). The commonest cause of infusion failure was superficial phlebitis: 47 per cent in the control group and 17 per cent in the treatment group (chi 2 = 46, P less than 0.0005). The estimated median time of infusion survival was 74 h in the control group compared with 127 h in the treatment group (log rank chi 2 = 143, P less than 0.0001). We conclude that infusion phlebitis is a common problem in hospitalized patients and its incidence can be effectively reduced by transdermal glyceryl trinitrate.

Naftidrofuryl and the nitrogen, carbohydrate, and lipid responses to moderate surgery.

The effect of twice daily infusions of 200 mg naftidrofuryl on the six day cumulative losses of urinary nitrogen after moderate surgery was studied in 32 patients maintained on an intravenous infusion of 4% dextrose and saline. A previous report of the ability of naftidrofuryl to reduce loss of nitrogen was not substantiated, although changes in metabolism in the immediate postoperative period suggested that the drug might exert some advantageous metabolic effect. Further investigations with other nutritional regimens are warranted.

A controlled study of single dosage cefamandole in the prophylaxis of wound infections in appendectomy.

A series of 102 consecutive patients undergoing appendectomy through an incision in the right iliac fossa entered a prospective randomized trial to compare the effects of a 2 gram intravenous bolus dose of cefamandole with a control study. No differences occurred in the incidence of wound infection in the two groups. We conclude that there is no place for a single preoperative dosage of cefamandole in the management of appendicitis.