Results of blood and plasma albumin tests for patients receiving dialysis have shown worryingly inconsistent results, according to new research published in Clinical Chemistry.
The inconsistency between testing methods leaves doctors to make important patient-care decisions based on potentially inaccurate information, and thus has the potential to make patients with kidney disease pay for unnecessary nutritional supplements.
The researchers, who are based at the UVA School of Medicine and Virginia Commonwealth University, are calling for revisions to federal guidelines to address the discrepancies and improve care for patients with end-stage kidney disease and other conditions.
“We base [many] of our decisions on lab parameters, and they have to be as accurate as possible,” said Emaad Abdel-Rahman, PhD, MBBS, nephrologist with the University of Virginia Health System. “Obviously, this puts a shadow on the results, and these are not as clear as they should be. You don't really know how to base a decision.”
The study involved 24 testing methods offered by various companies to analyze serum and plasma albumin in patients receiving dialysis. These levels are used to evaluate nutritional status, kidney function, and fluid balance. Results showed “significant” differences among the tests, and the researchers concluded that the inconsistency is compromising the interpretation of the results.
The two main classes of testing methods, bromocresol green (BCG) and bromocresol purple (BCP), were analyzed. None of the BCG methods evaluated met minimum performance specifications, while 8 of 12 BCP methods did. The four BCP methods that did not meet the performance standards generally had smaller biases when compared with the BCG methods, which skewed high.
David Bruns, MD, of the UVA Department of Pathology, explained that patients who do not meet albumin goals must receive nutritional interventions, which can be expensive. The inconsistent lab results can place another burden on patients who typically have plenty of burdens already.
“Nephrologists follow albumin results closely because the results are going to tell them if they need to do anything extra for these patients,” he said. “We know for a fact that [albumin levels] correlate with mortality. National guidelines define what is an acceptable range and what is not acceptable.”
UVA researcher Min Yu, MD, PhD, noted that the team was surprised by the wide spread in the testing results. “I don’t think we quite expected [the spread] to be this huge,” she said.
Study authors suggest that physicians should consider using the BCP methods exclusively to obtain more consistent results. Most testing companies, they noted, offer both BCG and BCP.
In addition, the researchers recommend that the federal Centers for Medicare and Medicaid Services revisit its guidelines for care of dialysis patients to reflect the variation in testing methods. Current standards call for serum albumin concentrations of at 4 g/dL when using a BCG method, but the new research shows that the BCG methods do not agree with each other. Patients with a serum albumin concentration less than 3.5 g/dL via BCG must receive protein supplementation. For BCP methods, the standard applied is the lower limit of “lab normal,” instead of the 3.5 g/dL threshold.
The goal of 4 g/dL was met by 32% of samples using one BCG method, while another found that only 13% of samples met the goal. For the 3.5 g/dL benchmark, 70% of samples reached the goal using one method, compared to 36% using another.
“Clearly, the use of quality goals at fixed concentrations is not tenable with the current state of harmonization of albumin methods,” the researchers concluded.