The need for a point of care testing: An evidence-based appraisal

A systematic evaluation of immunoassay point-of-care testing to define impact on patients' outcomes

Background Point-of-care testing has been developed to provide rapid test results. Most published studies focus on analytical performance, neglecting its impact on patient outcomes. Objective To review the analytical performance and accuracy of point-of-care testing specifically planned for immunoassay and to evaluate the impact of faster results on patient management. Methods A search of electronic databases for studies reporting immunoassay results obtained in both point-of-care testing and central laboratory scenarios was performed. Data were extracted concerning the study details, and the methodological quality was assessed. The analytical characteristics and diagnostic accuracy of six points-of-care testing: troponin, procalcitonin, parathyroid hormone, brain natriuretic peptide, C-reactive protein and neutrophil gelatinase-associated lipocalin were evaluated. Results A total of 116 scientific papers were analysed. Studies measuring procalcitonin, parathyroid hormone and neutrophil gelatinase-associated lipocalin reported a limited impact on diagnostic decisions. Seven studies measuring C-reactive protein claimed a significant reduction of antibiotic prescription. Several authors evaluated brain natriuretic peptide or troponin reporting faster decision-making without any improvement in clinical outcome. Forty-four per cent of studies reported analytical data, showing satisfactory correlations between results obtained through point-of-care testing and central laboratory setting. Half of studies defined the diagnostic accuracy of point-of-care testing as acceptable for troponin (median sensitivity and specificity: 74% and 94%, respectively), brain natriuretic peptide (median sensitivity and specificity: 82% and 88%, respectively) and C-reactive protein (median sensitivity and specificity 85%). Conclusions Point-of-care testing immunoassay results seem to be reliable and accurate for troponin, brain natriuretic peptide and C-reactive protein. The satisfactory analytical performance, together with an excellent practicability, suggests that it could be a consistent tool in clinical practice, but data are lacking regarding the patient outcomes.

Assessing Performance of i-STAT at the Point of Care in the Emergency Room

Context:

Point-of-care testing (POCT) for blood gas and chemistries is widely adopted in the emergency department (ED) for fast turnaround and critical medical decisions.

Objective:

To assess performance of ED physicians compared to laboratory technologists carrying out i-STAT analysis. Impact of user skill on POCT performance was also studied.

Design:

Over a 3-month period, ED physicians performed tests with their i-STAT unit with parallel blood specimens (n=60) sent to the central laboratory to be tested on another i-STAT unit and laboratory analysers (blood gas and chemistries). Comparisons to laboratory results (obtained with ABL 520 and Beckman-Coulter LX20PRO) were carried out. Two operators from ED and central laboratory performed side by side, repeated tests on the i-STAT units. Their overall within-run imprecision were compared. The analytical performance of i-STAT was further assessed by another laboratory technologist to verify its capability to deliver good results.

Results:

Platform comparisons showed that ED physicians performed poorer compared to laboratory technologists, particularly with chloride and pO2 (Spearman coefficient of correlation — 0.49 and 0.54 respectively indicate wide scatter). This is also mirrored in the higher overall within-run imprecision for chemistries (sodium, chloride, potassium, glucose, urea and creatinine) by an ED physician (5.4%) compared to a laboratory technologist (3.7%). Including blood gas results showed an even wider gap in their testing skills. Except at a low creatinine of 67 μmol/L, the i-STAT analyser delivered precise measurements for the chemistries and blood gas parameters.

Conclusions:

Performances by medical staff with the i-STAT analyser did not adequately approach the same skill level as laboratory technologists.

Decreasing lab turnaround time improves emergency department throughput and decreases emergency medical services diversion: a simulation model

BACKGROUND

The effect of decreasing lab turnaround times on emergency department (ED) efficiency can be estimated through system-level simulation models and help identify important outcome measures to study prospectively. Furthermore, such models may suggest the advantage of bedside or point-of-care testing and how they might affect efficiency measures.

OBJECTIVES

The authors used a sophisticated simulation model in place at an adult urban ED with an annual census of 55,000 patient visits. The effect of decreasing turnaround times on emergency medical services (EMS) diversion, ED patient throughput, and total ED length of stay (LOS) was determined.

METHODS

Data were generated by using system dynamics analytic modeling and simulation approach on 90 separate days from December 2, 2007, through February 29, 2008. The model was a continuous simulation of ED flow, driven by real-time actual patient data, and had intrinsic error checking to assume reasonable goodness-of-fit. A return of complete laboratory results incrementally at 120, 100, 80, 60, 40, 20, and 10 minutes was compared. Diversion calculation assumed EMS closure when more than 10 patients were in the waiting room and 100% ED bed occupancy had been reached for longer than 30 minutes, as per local practice. LOS was generated from data insertion into the patient flow stream and calculation of time to specific predefined gates. The average accuracy of four separate measurement channels (waiting room volume, ED census, inpatient admit stream, and ED discharge stream), all across 24 hours, was measured by comparing the area under the simulated curve against the area under the measured curve. Each channel's accuracy was summed and averaged for an overall accuracy rating.

RESULTS

As lab turnaround time decreased from 120 to 10 minutes, the total number of diversion days (maximum 57 at 120 minutes, minimum 29 at 10 minutes), average diversion hours per day (10.8 hours vs. 6.0 hours), percentage of days with diversion (63% vs. 32%), and average ED LOS (2.77 hours vs. 2.17 hours) incrementally decreased, while average daily throughput (104 patients vs. 120 patients) increased. All runs were at least 85% accurate.

CONCLUSIONS

This simulation model suggests compelling improvement in ED efficiency with decreasing lab turnaround time. Outcomes such as time on EMS diversion, ED LOS, and ED throughput represent important but understudied areas that should be evaluated prospectively. EDs should consider processes that will improve turnaround time, such as point-of-care testing, to obtain these goals.

Use of a quantitative point-of-care test for the detection of serum cardiac troponin T in patients with suspected acute coronary syndromes

We compared a third generation quantitative cardiac troponin T (cTnT) point-of-care testing (POCT) from Roche Diagnostics with the laboratory assay (Roche Elecsys 2010 immunoassay analyser). Heparin-treated blood and serum were collected simultaneously in 133 unselected patients (mean age 62 +/- 14 years, 38% females) presenting to our hospital with possible cardiac chest pain. Results of the POCT were measured against the laboratory-based assay considered as the gold standard. There were 18 POCT positive versus 24 laboratory assay positive (> or = 0.03 ng/mL) patients. POCT was falsely negative in six patients, with values between 0.03 and 0.1 ng/mL. The POCT had a sensitivity of 75%, specificity of 100%, positive predictive value of 100%, negative predictive value of 95% and a total accuracy of 95%; kappa = 0.831 (P < 0.001). There was good correlation between the values of POCT and the laboratory assay: Y = 1.195X + 0.002, r2 = 0.94 (P < 0.0001). Whereas cTnT levels > 0.1 mg/mL were reliably detected with this current generation of POCT, cTnT levels between 0.03 and 0.10 ng/mL were not. Future generations of devices will need to improve sensitivity to reliably risk stratify patients with suspected acute coronary syndromes.

Point-of-care testing in the United Kingdom

Point-of-care testing in the United Kingdom is currently at the embryo stage of development, and is approximately 10 years behind the United States in incorporation and application into clinical practice. Safeguards to ensure proper use are not in place within the UK at present, and there is no legal requirement for POCT users to be proficiency tested by an internal or external body before they can routinely use the equipment. Internal quality control and external quality assessment are not statutory requirements within the UK, leading to unease regarding the extent and range of point-of-care tests offered and whether the results are a true biochemical representation of the patient's clinical condition. Cost-benefit analysis is very sparse, but faster turnaround times can only lead to more rapid treatment of the patient, which will lead to fewer clinical complications. This will result in decreased hospital admissions by the emergency department and reduced length of hospital stay in ward-based patients. National Health Service (NHS) accountants will see this, as the way forward, as fewer patients being admitted into hospital and length of stay reduction will result in decreased expenditure by the service provider.

Ingenuous interpretation of elevated blood levels of macromolecular markers of myocardial injury: a recipe for confusion

Several assumptions about elevations of macromolecular markers of myocardial injury in blood require critical consideration. The dichotomy of modest, persistent elevations of troponins I and T as prognostic factors in patients with unstable angina and absent elevations of isoenzymes of creatine kinase is presently unexplained. Factors influencing the appearance of macromolecular markers of myocardial injury in blood are considered, including the need to estimate baseline values, to consider elevations as deviations from baseline rather than simply points within a distribution of baseline values in normal subjects, to recognize operative biochemical and physiologic determinants of marker release from injured myocytes and washout and to take into account the influence of apoptosis. Elucidation and consideration of mechanisms underlying the appearance of specific macromolecular markers in blood appear likely to improve diagnosis and explain the prognostic power of the troponins in patients with unstable angina. Detection of proteolytic breakdown products of troponins in blood is likely to explain the modest, persistent elevations seen in some patients with unstable angina and their prognostic implications.