How critical are critical values?

Outcome-Based Critical Result Thresholds in the Adult Patient Population

OBJECTIVES

To derive outcome-based critical result thresholds in the adult patient population.

METHODS

We extracted deidentified laboratory results and outcomes (death or discharged) of patients 18 years and older from the Medical Information Mart for Intensive Care database. The lower and upper critical result thresholds were obtained from the nearest minimum and maximum laboratory values, which corresponded to predicted probability of death at 90%.

RESULTS

The critical value thresholds were sodium (<123, >153 mmol/L), potassium (<2.2, >6.6 mmol/L), bicarbonate (<15, >49 mmol/L), chloride (<82, >121 mmol/L), urea (>20 mmol/L), creatinine (>1,052 μmol/L), glucose (<1.5, >23.8 mmol/L), total calcium (<1.62, >2.95 mmol/L), magnesium (<0.37, >1.48 mmol/L), phosphate (<0.19, >2.52 mmol/L), pH (<7.22, >7.57), lactate (>5.0 mmol/L), hemoglobin (<4.6 g/dL), WBCs (>32 × 103/μL), prothrombin time (>90 seconds), and international normalized ratio (>10).

CONCLUSIONS

The indirect approach described in this study is a pragmatic way to obtain threshold values that are clinically and operationally meaningful.

Relative criticalness of common laboratory tests for critical value reporting

We determined the relative strengths of association between 23 most commonly ordered laboratory tests and the adverse outcome as indicators of relative criticalness. The lowest and highest results for 23 most commonly ordered laboratory tests, 24 hours prior to death during critical care unit (CCU) stay or discharge from CCU were extracted from a publicly available CCU database (Medical Information Mart for Intensive Care-III). Following this, the Random Forest model was applied to assess the association between the laboratory results and the outcomes (death or discharge). The mean decrease in Gini coefficient for each laboratory test was then ranked as an indication of their relative importance to the outcome of a patient. In descending order, the 10 laboratory tests with the strongest association with death were: bicarbonate, phosphate, anion gap, white cell count (total), partial thromboplastin time, platelet, total calcium, chloride, glucose and INR; moreover, the strength of association was different for critically high versus low results.

Derivation of Outcome-Based Pediatric Critical Values

OBJECTIVES

There is currently a lack of an outcomes-based definition of critical values for the pediatric population. This has contributed to a highly heterogeneous critical value reporting practice between laboratories.

METHODS

Anonymized results were extracted from a laboratory information system for 10 biochemistry tests. The probability of high-dependency/intensive care unit admission (as a proxy for adverse outcomes) for each individual laboratory concentration was calculated and adjusted to fit using a polynomial function to model the probability trend. The laboratory value that intersected the 90% probability trend line was considered the critical value threshold.

RESULTS

The critical value thresholds for the serum analytes were sodium (mmol/L: <131, >148), potassium (mmol/L: <2.4, >6.4), bicarbonate (mmol/L: <13, >37), chloride (mmol/L: <91, >115), urea (mmol/L: >12), creatinine (μmol/L: >129), glucose (mmol/L: >17.2), total calcium (mmol/L: <1.9), magnesium (mmol/L: <0.6, >1.2), and phosphate (mmol/L: <0.4, >2.6).

CONCLUSIONS

This study described an approach to derive contemporary pediatric critical value thresholds.

Effectiveness of automated notification and customer service call centers for timely and accurate reporting of critical values: a laboratory medicine best practices systematic review and meta-analysis

OBJECTIVE

To conduct a systematic review of the evidence available in support of automated notification methods and call centers and to acknowledge other considerations in making evidence-based recommendations for best practices in improving the timeliness and accuracy of critical value reporting.

DESIGN AND METHODS

This review followed the Laboratory Medicine Best Practices (LMBP) review methods (Christenson, et al. 2011). A broad literature search and call for unpublished submissions returned 196 bibliographic records which were screened for eligibility. 41 studies were retrieved. Of these, 4 contained credible evidence for the timeliness and accuracy of automatic notification systems and 5 provided credible evidence for call centers for communicating critical value information in in-patient care settings.

RESULTS

Studies reporting improvement from implementing automated notification findings report mean differences and were standardized using the standard difference in means (d=0.42; 95% CI=0.2-0.62) while studies reporting improvement from implementing call centers generally reported criterion referenced findings and were standardized using odds ratios (OR=22.1; 95% CI=17.1-28.6).

CONCLUSIONS

The evidence, although suggestive, is not sufficient to make an LMBP recommendation for or against using automated notification systems as a best practice to improve the timeliness of critical value reporting in an in-patient care setting. Call centers, however, are effective in improving the timeliness of critical value reporting in an in-patient care setting, and meet LMBP criteria to be recommended as an "evidence-based best practice."

Critical values in cytology

The concept of critical values (CVs) is well established in clinical pathology, and has only recently been suggested in surgical pathology. To evaluate CVs in cytology, we reviewed 2,000 cytology reports at two large academic medical centers. Cases considered CV included unexpected malignancy, disagreement between immediate interpretation and final diagnosis in fine-needle aspirations (FNAs), and evidence of microorganisms in non-gynecology (non-GYN) and FNA specimens. We identified 52 CV cases (2.6%), including 0.25% (1/400) GYN, 1.88% (15/800) non-GYN, and 4.5% (36/800) FNA. Most of these (42 cases) were unexpected malignancies. Documentation of physician notification was present in 30 out of 52 cases. We also did a survey with 22 cytopathologists and 13 clinicians at large academic medical centers. The participants were asked to rate 18 different possible CVs from 1 to 3 as follows: (1) no phone call necessary, (2) phone call within 24 hr, (3) phone call as soon as possible (ASAP). Participants could also list additional diagnoses they believed constituted a CV. Most respondents agreed on the need for a phone call ASAP in many situations, and important additional CV cases were suggested. We suggest that a consensus conference of leaders in anatomic pathology and clinicians might prove useful to propose guidelines for CVs in cytology.

Communicating Critical Test Results: Safe Practice Recommendations

BACKGROUND

Massachusetts hospitals have collaborated in a patient safety initiative conducted by the Massachusetts Coalition for the Prevention of Medical Errors and the Massachusetts Hospital Association which is aimed at improving the ability to communicate critical test results in a timely and reliable way to the clinician who can take action. Solutions to this problem would address enhancing communication, teamwork, and information transfer, all fundamental system factors linked to patient safety. DEVELOPING THE SAFE PRACTICE RECOMMENDATIONS AND THE "STARTER SET": A Coalition-convened Consensus Group defined critical test results as values/interpretations for which reporting delays can result in serious adverse outcomes for patients. The scope included laboratory, cardiology, radiology, and other diagnostic tests in inpatient, emergency, and ambulatory settings. The Consensus Group developed Safe Practice Recommendations to promote successful communication of results, and a "starter set" of test results sufficiently abnormal to be widely agreed to be considered "critical."

DISSEMINATION

The recommendations and the starter set of test results were disseminated in a statewide collaborative open to all Massachusetts hospitals. Hospitals' team members tested changes and shared successful strategies that improved the reliability of communicating critical test results. An evaluation of the results of this collaborative is underway.

Laboratory critical values policies and procedures: a college of American Pathologists Q-Probes Study in 623 institutions

CONTEXT

Critical values lists have been used for many years to decide when to notify physicians and other caregivers of potentially life-threatening situations; however, these lists have not been studied widely.

OBJECTIVES

To investigate critical values lists in institutions participating in the College of American Pathologists Q-Probes program and to provide suggestions for improvement.

SETTING

A total of 623 institutions voluntarily participating in the Q-Probes program.

DESIGN

A multipart study in which participants responded to information from preprinted lists, collected information about current practices, completed a questionnaire, monitored critical values calls, reviewed patients' medical records, and surveyed nursing supervisors and physicians about critical values.

MAIN OUTCOME MEASURES

Defining critical values systems, including lists, personnel, costs, processes, usefulness, and related medical outcomes.

RESULTS

Critical values lists were determined for routine chemistry and hematology analytes and were found to vary widely among participants. In contrast, more than 95% of participants reported positive blood cultures, cerebrospinal fluid cultures, and toxic therapeutic drug levels as critical values. Based on more than 13 000 critical values, participants' data showed that most critical values reports (92.8%) were made by the person who performed the test, and that 65% of reports for inpatients were received by nurses. For outpatients, physicians' office staff received the largest percentage (40%) of reports. The majority of participants (71.4%) had no policy on how repeat critical calls should be handled. On average, completion of notification required about 6 minutes for inpatients and 14 minutes for outpatients. Slightly greater than 5% of critical value telephone calls were abandoned, with the largest percentage abandoned for outpatients. More than 45% of critical values were unexpected, and 65% resulted in a change in therapy. Although only 20.8% of 2301 nursing supervisors thought critical values lists were helpful, 94.9% of 514 physicians found critical values lists valuable.

CONCLUSIONS

Critical values systems were medically important, highly variable, but also costly practices for participants. We propose a number of recommendations for improvement, including that the critical values list should be approved by the medical staff, each laboratory should develop a written policy for handling initial and repeat critical values reports, a foolproof policy should be established to report results from calls abandoned, and efforts at automating the process should become widespread.