Can Urine Dipstick be Used as a Surrogate for Serum Creatinine in
Emergency Department Patients Who Undergo Contrast Studies?
Daniel Firestone, MD; Adam Wos, MD; James P. Killeen, MD; Theodore C. Chan, MD; Kama Guluma, MD; Daniel P. Davis, MD; Gary M. Vilke, MD
Emergency Department Patients Who Undergo Contrast Studies?
Daniel Firestone, MD; Adam Wos, MD; James P. Killeen, MD; Theodore C. Chan, MD; Kama Guluma, MD; Daniel P. Davis, MD; Gary M. Vilke, MD
Abstract
Contrast-induced nephropathy (CIN) is a complication associated with contrasted computed tomography (CT). Elevated creatinine (Cr) is often used to screen for CIN. This study evaluates dipstick urinalysis (Udip) detection of Cr > 1.5 mg/dL. If sufficiently sensitive, Udip results could then be incorporated into future rapid screening protocols for patients undergoing contrast studies. This retrospective record review evaluated all Emergency Department patients over 2 years with documented Udip and serum creatinine results. Patient demographics and pertinent past medical history were also collected. Data were collected on 2421 patient visits, with 241 having Cr > 1.5 mg/dL (9.9%).
There were 923 patient visits with a negative Udip (38.1%). Sensitivity and negative predictive value for abnormal Udip in detecting elevated creatinine were 85.5% and 96.2% (p < 0.01), respectively. Thirty-five patient visits (among 26 patients) had negative urine dip and Cr > 1.5 mg/dL, but each reported at least one of the following at triage: prior renal disease, hypertension, diabetes, congestive heart failure, or age > 60 years. Udip is a sensitive screening test, but alone is not accurate enough to predict patients at potential risk for CIN (Cr > 1.5 mg/dL). However, combining Udip results with risk factor screening may allow a rapid method for predicting which patients may safely undergo contrast CT scanning in the ED, but this needs prospective evaluation.
Contrast-induced nephropathy (CIN) is a complication associated with contrasted computed tomography (CT). Elevated creatinine (Cr) is often used to screen for CIN. This study evaluates dipstick urinalysis (Udip) detection of Cr > 1.5 mg/dL. If sufficiently sensitive, Udip results could then be incorporated into future rapid screening protocols for patients undergoing contrast studies. This retrospective record review evaluated all Emergency Department patients over 2 years with documented Udip and serum creatinine results. Patient demographics and pertinent past medical history were also collected. Data were collected on 2421 patient visits, with 241 having Cr > 1.5 mg/dL (9.9%).
There were 923 patient visits with a negative Udip (38.1%). Sensitivity and negative predictive value for abnormal Udip in detecting elevated creatinine were 85.5% and 96.2% (p < 0.01), respectively. Thirty-five patient visits (among 26 patients) had negative urine dip and Cr > 1.5 mg/dL, but each reported at least one of the following at triage: prior renal disease, hypertension, diabetes, congestive heart failure, or age > 60 years. Udip is a sensitive screening test, but alone is not accurate enough to predict patients at potential risk for CIN (Cr > 1.5 mg/dL). However, combining Udip results with risk factor screening may allow a rapid method for predicting which patients may safely undergo contrast CT scanning in the ED, but this needs prospective evaluation.
Introduction
Patients who present to the Emergency Department (ED) commonly require intravenous (i.v.) contrast for computed tomography (CT) scans. Contrast-induced nephropathy (CIN) is a potential complication of intravenous contrast administration. In the general population, the incidence of CIN is estimated to be 1 6%. However, the risk may be as high as 50% in somepatient subgroups.[1]
There are more than one million contrast studies performed in the United States each year, with approximately 150,000 cases of CIN occurring annually. Contrast-induced nephropathy is the third most common cause of hospital-acquired renal failure, with about 1% of these hospitalized cases requiring dialysis. The development of CIN increases average length of stay in hospitals by 2 additional days. In the critical care population, in-house mortality rate has been described at 36%, with 19% survival rate at 2 years.[2] In general, most cases of CIN resolve without the need for treatment, but there is a 0.5 2.0% risk of needing dialysis associated with the development of CIN among all patients.
Certain populations seem to be at risk for developing CIN. These include patients with pre-existing renal impairment, diabetes, hypertension, congestive heart failure, advanced age, volume depletion, use of nephrotoxic medications, and large volume or high osmolality of the contrast agent.[3]
Contrast-induced nephropathy risk increases as glomular filtration rate (GFR) decreases in a curvilinear fashion. A breakpoint for increased risk of CIN is found at GFR < 60 mL/min/1.73 m2. This correlates with a serum creatinine of > 1.5 mg/dL. Other surrogates for abnormal GFR include 24-h urine protein collection and spot urine protein-to-creatinine ratio. Both of these have either time or cost limitations for conventional ED applications. For its relative simplicity, the serum creatinine is used at many hospitals to determine whether a patient is a candidate for i.v. contrast administration, with a serum creatinine of 1.5 mg/dL or greater being considered a contraindication to contrast dye due to the presumed increased risk of contrast-induced nephropathy. Radiology protocols often require obtaining a serum creatinine before a contrast study can be performed. This may cause delays in diagnosis and patient throughput times in the ED.
Urine dipstick (Udip) has been used successfully as a screening test for serum creatinine elevation in ED patients with severe hypertension.[4] Specifically, proteinuria and hematuria on dipstick urinalysis correlate with impaired renal function. Karras et al. found that the Udip was 96% sensitive and 87% specific for detection of significant proteinuria.[4] It was 91 100% sensitive and 65 99% specific for detection of microscopic hematuria. Point-of-care proteinuria or hematuria identified 100% of severely hypertensive patients with Cr > 1.2 mg/dL in one ED study.[4]
This study was designed to determine if the urine dipstick can reliably detect an elevation in serum creatinine > 1.5 mg/dL in a whole population of ED patients. Serum creatinine is an imperfect surrogate, only in part due to the delay in acquiring and acting on the laboratory test results in real ED time. Its prevalence in radiology protocols warrants the design of more efficient ways for screening for occult elevated values. This phase one study is intended to be followed by a prospective study that will test a more exhaustive screening protocol for patients at risk for CIN.
DOWNLOAD PDF COMPLETE HERE
Patients who present to the Emergency Department (ED) commonly require intravenous (i.v.) contrast for computed tomography (CT) scans. Contrast-induced nephropathy (CIN) is a potential complication of intravenous contrast administration. In the general population, the incidence of CIN is estimated to be 1 6%. However, the risk may be as high as 50% in somepatient subgroups.[1]
There are more than one million contrast studies performed in the United States each year, with approximately 150,000 cases of CIN occurring annually. Contrast-induced nephropathy is the third most common cause of hospital-acquired renal failure, with about 1% of these hospitalized cases requiring dialysis. The development of CIN increases average length of stay in hospitals by 2 additional days. In the critical care population, in-house mortality rate has been described at 36%, with 19% survival rate at 2 years.[2] In general, most cases of CIN resolve without the need for treatment, but there is a 0.5 2.0% risk of needing dialysis associated with the development of CIN among all patients.
Certain populations seem to be at risk for developing CIN. These include patients with pre-existing renal impairment, diabetes, hypertension, congestive heart failure, advanced age, volume depletion, use of nephrotoxic medications, and large volume or high osmolality of the contrast agent.[3]
Contrast-induced nephropathy risk increases as glomular filtration rate (GFR) decreases in a curvilinear fashion. A breakpoint for increased risk of CIN is found at GFR < 60 mL/min/1.73 m2. This correlates with a serum creatinine of > 1.5 mg/dL. Other surrogates for abnormal GFR include 24-h urine protein collection and spot urine protein-to-creatinine ratio. Both of these have either time or cost limitations for conventional ED applications. For its relative simplicity, the serum creatinine is used at many hospitals to determine whether a patient is a candidate for i.v. contrast administration, with a serum creatinine of 1.5 mg/dL or greater being considered a contraindication to contrast dye due to the presumed increased risk of contrast-induced nephropathy. Radiology protocols often require obtaining a serum creatinine before a contrast study can be performed. This may cause delays in diagnosis and patient throughput times in the ED.
Urine dipstick (Udip) has been used successfully as a screening test for serum creatinine elevation in ED patients with severe hypertension.[4] Specifically, proteinuria and hematuria on dipstick urinalysis correlate with impaired renal function. Karras et al. found that the Udip was 96% sensitive and 87% specific for detection of significant proteinuria.[4] It was 91 100% sensitive and 65 99% specific for detection of microscopic hematuria. Point-of-care proteinuria or hematuria identified 100% of severely hypertensive patients with Cr > 1.2 mg/dL in one ED study.[4]
This study was designed to determine if the urine dipstick can reliably detect an elevation in serum creatinine > 1.5 mg/dL in a whole population of ED patients. Serum creatinine is an imperfect surrogate, only in part due to the delay in acquiring and acting on the laboratory test results in real ED time. Its prevalence in radiology protocols warrants the design of more efficient ways for screening for occult elevated values. This phase one study is intended to be followed by a prospective study that will test a more exhaustive screening protocol for patients at risk for CIN.
DOWNLOAD PDF COMPLETE HERE
0 comments
Post a Comment