Clinical laboratory testing in the emergency department: a six-year analysis

Introduction

Clinical laboratory services are crucial in emergency departments as they provide timely and accurate diagnostic information to aid in the assessment and management of patients. Early detection of life-threatening conditions and guide appropriate treatment decisions may be provided with rapid laboratory tests. There were one hundred thirty million emergency department visits in the USA annually in 2019, which is reflected in the statistics as one hundred seven million in our country in 2017 [1]. In emergency departments, not only for diagnosis, clinical laboratory tests are used to exclude the differential diagnosis, follow up, and evaluate the response to treatment. With their own units, clinical laboratory results can be accessed more easily in emergency departments; thus, decision-making for discharge or hospitalization can be made faster with the aid of these tests.

The most frequently used clinical laboratory tests in emergency departments were complete blood count (CBC), kidney function tests, liver function tests, acute phase reactants, and electrolytes [2]. Especially in preliminary diagnoses such as trauma and bleeding, laboratory services play a significant role in determining the need for blood product support in the emergency department, monitoring bleeding, and identifying changes in CBC parameters following transfusion [3]. Coagulation tests such as prothrombin time (PT), partial thromboplastin time (aPTT), and international normalized ratio (INR) are required for the etiology of bleeding and also help physicians choose the necessary treatment modalities [3]. The use of CBC and acute phase reactants, such as C-reactive protein (CRP), are used in the diagnosis of sepsis [4, 5]. In chronic diseases such as kidney failure, changes in blood urine nitrogen (BUN), creatinine (CREA), and blood gases results are particularly important to distinguish between acute and chronic conditions and determine whether urgent dialysis is necessary and follow-up for dialysis utility [6]. Moreover, changes in electrolyte levels, such as potassium, help confirm additional cardiac complications in those patients. Clinical laboratory tests are not only utilized as diagnostic tools but are also integrated into clinical risk scores to determine the severity or staging of the disease [7], [8], [9], [10].

In particular, the COVID-19 outbreak has caused a change in the number of patients in emergency departments. During the pandemic, the effectiveness of clinical laboratory tests such as D-dimer, fibrinogen, and ferritin has become crucial for the diagnosis of COVID-19 and the assessment of pneumonia severity [11, 12].

The use of clinical tests is increasing in emergency departments due to various reasons, such as the need for diagnosis, monitoring, and evaluation of treatment response. Analyzing laboratory test results, such as inflammation markers before and after the onset of COVID-19, would provide valuable scientific insight for healthcare delivery and planning. This study aimed to examine the utilization of clinical laboratory tests in the emergency department and to identify the trends and changes in their usage over six years covering the COVID-19 pandemic.

Materials and methods

Results

The number of emergency department visits and triage areas by year are shown in Figure 1. The total number of 92,611,024 in 2016 increased to 129,764,460 in 2019. With the COVID-19 outbreak in 2020, visits decreased by 27.89 % compared to 2019, and after 2020, visits reincreased at a rate of 38.50 % compared to 2020. Considering emergency department visits, the rate of visits in the yellow and red triage areas where diagnostic tests were mostly performed increased from 80.3 to 83.0 % (n=107,496,231) in 2021 (Table 1). The green triaged patients rate decreased from 19.7 to 17 % over time. The total number of tests requested per overall patients increased by 268.92 % from 2016 to 2021 (Table 1, Supplementary Material).

Figure 1:

Total number of visits to triage areas in emergency departments by year.

The frequently used clinical laboratory tests are shown in Table 2.

Rates of most commonly used tests overall were CBC (7.85 %), CREA (7.02 %), potassium (6.77 %), BUN (6.70 %), ALT (6.67 %), AST (6.64 %), and sodium (6.35 %), respectively (Figure 2). Biomarkers used in COVID-19 severity prediction as ferritin (1,210.30 %), D-dimer (1,180.95 %), fibrinogen (315.25 %), CRP (118.82 %), and albumin (35.69 %), showed an increasing pattern from 2016 to 2021 (Table 2). The only decrease was in urine tests from 2016 to 2021 (−31.79 %). Considering the pandemic, all laboratory test rates were changed negatively except D-dimer (617.09 %), ferritin (1,133.28 %), fibrinogen (276.45 %), CRP (6.03 %), LDH (9.57 %), troponin I (4.54 %), PT (23.31 %), aPTT (20.38 %), troponin T (6.55 %), sedimentation rate (114.10 %) were increased in 2020 when compared with 2019 (Figure 3).

Figure 2:

Distribution of the numbers of clinical laboratory test requests in emergency departments by year. CRP, C-reactive protein; BUN, blood urea nitrogen; Na, sodium; K, potassium; Ca, calcium; Cl, clor; AST, aspartate aminotransferase test; ALT, alanine aminotransferase test; ALP, alkaline phosphatase; GGT, gamma-glutamyl transferase; CK, creatine kinase; CK-MB, creatine kinase myocardial band; aPTT, activated partial thromboplastin time; PT, prothrombin time.

Figure 3:

The rate of change between consecutive years. CRP, C-reactive protein; BUN, blood urea nitrogen; Na, sodium; K, potassium; Ca, calcium; Cl, clor; AST, aspartate aminotransferase test; ALT, alanine aminotransferase test; ALP, alkaline phosphatase; GGT, gamma-glutamyl transferase; CK, creatine kinase; CK-MB, creatine kinase myocardial band; aPTT, activated partial thromboplastin time; PT, prothrombin time.

Although the decrease in overall CK-MB is predominantly observed in CK-MB (activity) (−9.79 %), CK-MB (mass) has relatively increased (67.37 %) over the six years (Table 2). A higher increase among cardiac biomarkers was seen in troponin T (226.27 %) throughout these years (Table 2). Troponin I was used more than troponin T in 2016 (4,194,176 vs. 1,089,300) and increased with a rate of 71.41 % over six years.

The mostly used electrolyte levels were K (6.77 %), Na (6.35 %), Ca (5.27 %), and Cl (4.66 %) among the tests, respectively.

Discussion

This study aimed to reveal the use of clinical laboratory tests in emergency departments and the change after the COVID-19 pandemic. We found that CBC, CREA, K, BUN, ALT, AST, and Na were the most commonly used clinical laboratory tests in emergency departments for all six years. Our findings indicated an increase in the use of particularly D-dimer, ferritin, and fibrinogen, in emergency departments, with a trend that may further increase in the coming years.

Emergency services are hospital units whose patient density and circulation change rapidly. Fast diagnosis and treatment are vital on the basis of 24-h service. Their collaboration with units such as laboratories is important to deliver high-quality healthcare [15]. Consistent with our study, it is seen that the use of diagnostic tests in the literature has increased [16, 17]. Nazerian et al. has found that optimization of test profiles and education reduced test ordering and provided appropriate test use [16].

The most commonly used test may be the result of patient follow-up in emergency departments. Patient follow-up in emergency departments may result in laboratory retesting. Although retests are performed for patients whose length of stay is prolonged, the duration of stay may be prolonged due to the requirement of repetitive laboratory tests [18], [19], [20]. Although retesting is used to determine the response to treatment (such as creatine and blood gases after dialysis or hemoglobin level after blood transfusion), no conclusion was drawn in our study since there were no retesting rates and numbers. More than one test per patient, such as in patients whose hemoglobin levels are followed up in the emergency department for reasons such as trauma and gastrointestinal bleeding or the follow-up of Cr and potassium values in terms of evaluating the response to treatment in the follow-up of acute renal failure in the emergency department. In a randomized controlled study, point-of-care testing did not reduce time; however, it reduced the time to result [21].

Using biochemical markers for defensive medicine also increases the risk and cost [22, 23]. Numbers and changes in complete blood count, CRP, renal and liver function tests, including CREA, BUN, AST, and ALT, showed similar trends (Figure 2). This may be due to the simultaneous ordering of these tests, as stated in the literature [23]. Cadamuro et al. revealed that routine laboratory panel use reduces the re-ordering rate, especially from the emergency department [24].

In addition, it has been shown in the literature that routine blood tests (albumin, Cr, C-reactive protein, CBC, lactate dehydrogenase, leukocyte count, potassium, and sodium) improve risk stratification and predict mortality of patients admitted to the emergency department [25], [26], [27]. In our study, it was found that the most frequently requested examinations in our country were CBC, CREA, potassium, AST, and ALT. Therefore, our findings are also compatible with the literature [25].

We found that an increase in D-dimer and blood gas tests in the last two years may be due to complications related to thrombosis, especially lower respiratory tract involvement. There is a need for comparative correlational analysis on the subject in light of our findings.

Likewise, CK-MB use as a cardiac marker decreased after the updates of the American Heart Association/American College of Cardiology because the change in CK-MB levels is affected by many factors [28], [29], [30]. In our study, although it showed a 10.58 % decrease, CK-MB showed a decreasing trend within years, which needs further investigation with multicenter correlational analysis with admissions.

In addition to cardiac markers such as CK-MB, guidelines no longer recommend the use of CK-MB after the increasing replacement of hsTnT [31]. Additionally, hsTnT has been associated with cardiovascular mortality in subsequent cardiovascular events with atherosclerosis and in COVID-19 patients [31], [32], [33], [34], [35]. The increase in hsTnT and hsTnI might be due to these changes in the use of risk stratification of these patients. Besides, CK-MB use may be decreased according to the guidelines highlighting the unpractical use of CK-MB in acute cardiovascular diseases.

Blood gas analysis showed an increase of 189.40 % from 2016 to 2021. This may be due to the increased number of patients with low saturation admitted to emergency departments and their need for blood gas monitoring [36].

In addition, the reason for the decline behind some tests may be their removal from the electronic laboratory panel. In a study, the decrease in the number of sedimentation rate, fibrinogen, AST, Ca, and lipase tests occurred by removing these requests from the panel [37].

One of the important factors that change laboratory test requests is patient visit zones [38]. In one study, independent of diagnosis, there were significantly more test requests in the patients evaluated in the yellow zone [38]. In our study, the number of visits has been increased however, the rate of the green triaged patients has decreased. This decrease may be due to the increase in the emergency visits of patients with more life-threatening risks, as well as changing the patient triage according to the test requests.

Conclusions

The results of our study reveal that the most commonly ordered laboratory tests in the emergency department are CBC, CREA, potassium, BUN, AST, ALT, and Na. However, our analysis shows that the use of ferritin, fibrinogen, CRP, and D-dimer has increased in the last two years, likely due to their clinical usefulness in predicting the outcome of COVID-19. Our study focused on the changes in clinical laboratory testing over the past six years and the corresponding increase in test orders. Future research should investigate the underlying reasons and potential implications of this trend. It is important to our study provides a foundation for future investigations exploring the relationship between laboratory testing and necessity. Additionally, by identifying the most frequently used tests in the emergency department, our findings can facilitate efforts to streamline and optimize the use of resources, making the testing process more efficient.

Highlights

1. Rational laboratory usage is important in determining changes in test numbers.

2. Over the years, with the development of the pandemic and changes in guidelines, changes in laboratory tests have been observed. CBC, CREA, potassium, BUN, AST, ALT, and Na is the most commonly used emergency laboratory tests.

3. The use of ferritin, fibrinogen, CRP, and D-dimer has increased after the onset of the pandemic.