SAN DIEGO—The use of urine neutrophil gelatinase-associated lipocalin (NGAL), which has emerged as a promising marker for development of early acute kidney injury (AKI), could result in a substantial cost savings, according to researchers. These savings would accrue primarily because of reductions in the number of tests and time to treatment.
Amay Parikh, MD, MBA, MS, Thomas Nickolas, MD, MS, and two other investigators developed two models of testing strategies, one involving serum-creatinine testing alone and another involving the combination of serum creatinine and NGAL testing. For costs, they used data from the literature and a yet-to-be-published study they undertook of 849 patients with serum creatinine levels of 1.5 mg/dL or higher who were treated in the emergency department (ED) of New York Presbyterian’s Allen Hospital and Staten Island University Hospital.
“We used this level of serum creatinine as a cut-off because that is what is used in the ‘risk’ category in RIFLE (assuming a baseline creatinine of 1.0), except RIFLE also includes urine output,” explained Dr. Parikh, a fellow in critical care at Columbia University in New York. “We felt this was fair because in the ED when the patient comes in, they’re not going to be able to say how much urine they produced over the previous 24 hours.”
The investigators extrapolated from these subjects to a hypothetical cohort of 10,000 patients, and plugged in testing and hospitalization/ICU costs. They also factored in probabilities for a variety of parameters, from that of a patient not having elevated creatinine or NGAL, to the percent of patients with stable chronic kidney disease.
Results indicated that 1,578 fewer patients would have delayed diagnosis and treatment when NGAL and creatinine testing were both used compared with creatinine testing alone, using data from the Allen hospital. There would be 1,973 fewer patients with delayed diagnosis and treatment using data from the Staten Island hospital.
The model results also suggested costs would be $408 lower per patient using data from the Allen hospital and $522 lower per patient using data from the Staten Island hospital. Most of these savings originate from hospitalization-related costs.
The investigators varied the values of the variables used in the models and found that use of NGAL testing was consistently less expensive than use of serum creatinine testing alone.
Two researchers not involved in the study questioned the models used by Dr. Parikh and colleagues. “They used as a cut-off for a serum creatinine of 1.5 [mg/dL] or higher, but patients with lower creatinine may have AKI as well as chronic kidney disease, so this isn’t broadly applicable to the general population.,” observed Jay Koyner, MD, Assistant Professor of Medicine at the University of Chicago. “They also say serum creatinine [testing] costs $100 at both hospitals examined in the model and that NGAL [testing] costs $50. But creatinine is usually done as part of a panel and that’s what costs $100; creatinine itself should not cost that much. Additionally, NGAL, just like serum creatinine, needs to be measured serially in order to monitor patients and that increases the cost.”
Overall, he added, NGAL appears to reduce the number of tests required but not the length of hospital stay, since “$400 to $500 is only a fraction of one day’s hospital stay.”
Uptal Patel, MD, Assistant Professor of Medicine and Pediatrics in the Divisions of Nephrology and Pediatric Nephrology, Duke Clinical Research Institute, Durham, N.C., also noted that the costs the investigators use for creatinine and NGAL testing may have skewed the results in favor of NGAL. He also made an even more fundamental point.
“It is not clear how earlier detection of AKI will alter patient management in order to reduce hospitalization costs,” Dr. Patel said. “Although many promising therapies are being evaluated, we have not yet found effective therapies to improve outcomes for patients who develop AKI.”