Bedside diagnostic testing of body fluids

Porous bead-based diagnostic platforms: bridging the gaps in healthcare

Advances in lab-on-a-chip systems have strong potential for multiplexed detection of a wide range of analytes with reduced sample and reagent volume; lower costs and shorter analysis times. The completion of high-fidelity multiplexed and multiclass assays remains a challenge for the medical microdevice field; as it struggles to achieve and expand upon at the point-of-care the quality of results that are achieved now routinely in remote laboratory settings. This review article serves to explore for the first time the key intersection of multiplexed bead-based detection systems with integrated microfluidic structures alongside porous capture elements together with biomarker validation studies. These strategically important elements are evaluated here in the context of platform generation as suitable for near-patient testing. Essential issues related to the scalability of these modular sensor ensembles are explored as are attempts to move such multiplexed and multiclass platforms into large-scale clinical trials. Recent efforts in these bead sensors have shown advantages over planar microarrays in terms of their capacity to generate multiplexed test results with shorter analysis times. Through high surface-to-volume ratios and encoding capabilities; porous bead-based ensembles; when combined with microfluidic elements; allow for high-throughput testing for enzymatic assays; general chemistries; protein; antibody and oligonucleotide applications.

Point-of-Care Testing Reduces Length of Stay in Emergency Department Chest Pain Patients

STUDY OBJECTIVE

We determine the effect of cardiac troponin I point-of-care testing on emergency department (ED) length of stay in chest pain patients.

METHODS

This was a before-and-after trial in a university-based ED with 75,000 annual visits. Participants were consecutive patients with a chief complaint of chest pain who were admitted to the hospital. During the first 2-week period (before), only central laboratory testing of troponin was performed. During the second 2-week period (after), treating nurses performed bedside point-of-care testing for troponin I, as well as central laboratory testing. Test turnaround times, time from triage until calling in admissions, and time from triage until patients left the ED to be transferred to a floor (ED length of stay) were determined and compared between the 2 study periods. Comparisons between study periods are expressed as mean differences with 95% confidence intervals (CIs). A sample of 100 patients in each group had 90% power to detect a 1-hour difference in length of stay (2-tailed alpha=0.05).

RESULTS

There were 232 patients before and 134 after introduction of point-of-care testing. Mean age (SD) was 63 years (16 years), and 44% were female patients. Baseline characteristics were similar in both groups. The rate of positive troponins was also similar (9.5% versus 6.1%). ED length of stay was significantly reduced after introduction of point-of-care testing (5.2 hours [95% CI 4.6 to 5.8 hours] versus 7.1 hours [95% CI 6.6 to 7.7 hours]; mean difference 1.9 hours [95% CI 1.1 to 2.7 hours]). The time until the admission was called in to bed control was also significantly reduced by introducing point-of-care testing (2.7 hours [95% CI 2.4 to 3.1 hours] versus 4.7 hours [95% CI 4.3 to 5.0 hours]; mean difference 1.9 hours [95% CI 1.4 to 2.5 hours]). Point-of-care testing turnaround (14.8 minutes [95% CI 14.1 to 15.5 minutes]) was significantly shorter than for central laboratory testing (83 minutes [95% CI 77 to 89 minutes]; mean difference 68 minutes [95% CI 62 minutes to 74 minutes]). With central testing as the criterion standard, point-of-care testing had a sensitivity of 100% (95% CI 63% to 100%) and a specificity of 96% (95% CI 92% to 99%).

CONCLUSION

Bedside performance of troponin I point-of-care testing by treating nurses significantly reduces ED length of stay.

Implementation of a point-of-care satellite laboratory in the emergency department of an academic medical center. Impact on test turnaround time and patient emergency department length of stay

CONTEXT

Emergency department (ED) overcrowding has reached crisis proportions in the United States. Many hospitals are seeking to identify process reengineering efforts to reduce crowding and ED patient length of stay (LOS).

OBJECTIVES

To investigate the impact of a point-of-care testing (POCT) satellite laboratory in the ED of a large academic medical center.

SETTING

The ED of the Massachusetts General Hospital, Boston, Mass.

DESIGN AND OUTCOME MEASURES

Evaluation of physician satisfaction, turnaround time (TAT), and ED LOS before and after implementation of a POCT laboratory. ED LOS was measured by patient chart audits. TAT was assessed by manual and computer audits. Clinician satisfaction surveys measured satisfaction with test TAT and test accuracy.

RESULTS

Blood glucose, urine human chorionic gonadotropin, urine dipstick, creatine kinase-MB, and troponin tests were performed in the ED POCT laboratory. Test TAT declined an average of 87% after the institution of POCT. The ED LOS decreased for patients who received pregnancy testing, urine dipstick, and cardiac markers. Although these differences were not significant for individual tests, when the tests were combined, the decreased LOS was, on average, 41.3 minutes (P =.006). Clinician satisfaction surveys documented equivalent satisfaction with test accuracy between the central laboratory and the POCT laboratory. These surveys also documented dissatisfaction with central laboratory TAT and increased satisfaction with TAT of the POCT program (P <.001).

CONCLUSIONS

The POCT satellite laboratory decreased test TAT and decreased ED LOS. There was excellent satisfaction with test accuracy and TAT.

Reagent strip diagnosis of UTI in a high-risk population

A study was undertaken to determine the accuracy of reagent strip diagnosis of urinary tract infection (UTI) in patients seen in the ED who were subsequently admitted to hospital with this diagnosis. The reagent strip results of 100 patients were recorded and the sensitivity and specificity of various parameters in the diagnosis of UTI were calculated. Our results indicate that even in a group of patients with high clinical probability of UTI and with symptoms severe enough to be hospitalized, reliance on positivity of any single parameter alone gives unacceptably low sensitivity: 89%, 39%, 68%, and 63% for WBC, nitrite, RBC, and protein, respectively. We conclude that dipstick analysis is not sufficiently sensitive for diagnosis of UTI in high risk patients in whom missed diagnosis would have serious consequences.

Status of point-of-care testing: promise, realities, and possibilities

Point-of-care testing (POCT) has evolved from the demand for analytical information more rapidly than is available from central laboratories. By bringing the analysis closer to the patient several process steps have been eliminated, facilitating a shorter time to result and faster management response with improved outcomes. Thus benefits include better therapeutic turnaround times, decreased blood loss as a result of reduced phlebotomy secondary to clinical improvement, and diminished resource utilization. These advantages depend on acceptable analytical performance in comparison with central laboratory methods and in relation to clinical criteria. Generally these requirements are met but there are problems particularly with atypical specimens. Outcomes and cost-benefit analyses have been difficult to perform and evaluate. Given the multitude of participants, quality assurance and program management are recognized as resource intensive. However, recognition of problem areas is driving continuous improvement and we envisage expansion of this paradigm.