American Journal of Emergency Medicine 38 (2020) 2750-2751

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American Journal of Emergency Medicine

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The relationship between two laboratory assays: high sensitivity troponin T and N-terminal pro- brain natriuretic peptide

High sensitivity troponin T (hsTnT) is increasingly utilized in the emergency department (ED) to determine risk for acute coronary syn- drome (ACS). Several studies suggest that hsTnT is elevated in patients with congestive heart failure (CHF) [1-3]. The prevalence of elevated hsTnT, above 13.5 ng/L, in the setting of CHF was estimated to be 64.0% and 47.1% in the Val-HEFT and GISSI-HF trials, respectively [1- 3]. This study sought to examine the relationship between two labora- tory assays, hsTnT and N-terminal pro-brain natriuretic peptide (NT- proBNP), a marker for CHF, in patients presenting to the ED.

This retrospective cohort study was performed at a quaternary care academic hospital and an urban community hospital with 130,000 an- nual ED visits combined. Data was collected for a 10-month period, July 2017 to May 2018. Patients >=18 years were included if they had two serial hsTnTs, NT-proBNP, and serum creatinine measured within a 24-hour time-period during their ED visit. Only one encounter se- lected at random per patient was included. Patients with low estimated glomerular filtration rate (eGFRb60 mL/min/1.73 m²) as calculated using the CKD-EPI equation were excluded as previous studies have demonstrated abnormally high hsTnT values in patients with renal im- pairment [4,5]. Demographic information including age, race, and gen- der was collected.

Cochran-Armitage Trend test was used to evaluate whether the fre- quency of NT-proBNP elevation increased/decreased with increasing initial hsTnT values (low: b12 ng/L, intermediate: >=12 and b52 ng/L, high: >=52 ng/L). Cut-offs were determined as per hospital and European Society of Cardiology (ESC) guidelines [6]. NT-proBNP was considered elevated above 125 pg/mL, or above 450 pg/mL in ages

>=75 per hospital guidelines. NT-proBNP values among patients in the three hsTnT groups were compared using Kruskal-Wallis followed by Dunn All Pairs for Joint Ranks tests. Chi-square analysis was used to compare frequency of hsTnT elevation between patients with normal and elevated NT-proBNP. Statistical tests were performed using JMP Pro 14 statistical software (SAS Institute, Cary, NC).

1150 ng/L, respectively (P b .0001 for low versus intermediate and low versus high. No significant difference between intermediate and high). A similar relationship between hsTnT and NT-proBNP was seen among the subgroup of patients with serial 1-hour delta hsTnT b3 (Table 1).

We also compared the distribution of hsTnT among patients with normal versus elevated NT-proBNP. Among patients with normal NT- proBNP, 72% (257/359) had low hsTnT, 26% (94/359) had intermediate hsTnT, and 2% (8/359) had high hsTnT. In patients with elevated NT- proBNP, 31% (128/416) had low hsTnT, 57% (237/416) had intermediate hsTnT, and 12% (51/416) had high hsTnT, (P b .0001), (Table 1).

The results of this study suggest a significant positive correlation be- tween hsTnT and NT-proBNP. ED patients who presented with interme- diate or high hsTnT were at least twice as likely to have elevated NT- proBNP as patients with low hsTnT (74% v. 33%, respectively). Addition- ally, 69% of patients with an elevated NT-proBNP had intermediate or high hsTnT, compared to 28% of those with a normal NT-proBNP. It is possible that patients with elevated NT-proBNP, a potential laboratory marker for CHF, have elevated hsTnT at baseline. This could lead to ACS workups based on laboratory findings.

We also found that patients with elevated NT-proBNP in the inter- mediate or high hsTnT groups had a higher elevation of NT-proBNP (N1000 ng/L) than patients in the low hsTnT group (b400 ng/L). Numer- ous studies have shown high Nt-proBNP levels to have prognostic value in patients with ACS [7]. Perhaps higher NT-proBNP elevation also sug- gests that it is a contributing factor to elevated hsTnT values.

Due to the retrospective nature of this study, laboratory assays were ordered at the discretion of the ED physician and therefore may not rep- resent all patients with suspected ACS or CHF. Additionally, the findings cannot be reliably applied to patients with renal disease as we excluded patients with eGFR below 60 mL/min/1.73 m².

This study suggests a relationship between the hsTnT and NT- proBNP laboratory assays. Further studies are needed to examine how elevated hsTnT assays and NT-proBNP may influence clinical workups for rapid rule-out of ACS.

Table 1

Number of patients with normal versus elevated NT-proBNP compared to hsTNT values.

A total of 1298 encounters were evaluated. After excluding multiple visits (78) and low eGFR (445), the final cohort consisted of 775 en- counters. The mean age was 59 (SD 15) and median eGFR was 85 mL/ min/1.73 m² (SD 17). 51% of patients were female, 50% Caucasian, and 45% African-American. The most common chief complaints were chest

Total Low hsTnT

(b12 ng/L)

Intermediate hsTnT (>=12 and b52 ng/L)

High hsTnT (>=52 ng/L)

hsTnT, 72% (237/331) with intermediate hsTnT, and 86% (51/59) with high hsTnT had an elevated NT-proBNP (P b .0001), (Table 1). The me- dian NT-proBNP of all individuals with elevated NT-proBNP in the low, intermediate, and high hsTnT groups was 323 ng/L, 1291 ng/L, and

https://doi.org/10.1016/j.ajem.2020.04.074

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The relationship between two laboratory assays: High sensitivity troponin T and N-terminal pro-brain natriuretic peptide 2751

References

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   Andrew Singletary

   Case Western Reserve University School of Medicine, Cleveland, OH, United

   States of America

   Rakesh Engineer Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America c

   Amy S. Nowacki Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America d

   Baruch S. Fertel Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America Emergency Services Institute, Cleveland Clinic Health System, Cleveland,

   OH, United States of Americae

   Courtney M. Smalley Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America c

   Navkiranjot Kaur Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America

   ?Corresponding author.

   E-mail address: [email protected]

   23 April 2020