Christine L.H. Snozek

Prognostic value of the serum free light chain ratio in newly diagnosed myeloma: proposed incorporation into the international staging system

To determine if the serum free light chain (FLC) ratio has prognostic value in patients with symptomatic multiple myeloma (MM), baseline serum samples from a well-characterized cohort of 790 newly diagnosed MM patients were tested with the FLC assay. FLC ratio was calculated as κ/λ (reference range 0.26–1.65). On the basis of the distribution of values, a cutpoint κ/λ FLC ratio of <0.03 or >32 was chosen for further analysis. Overall survival was significantly inferior in patients with an abnormal FLC ratio of <0.03 or >32 (n=479) compared with those with an FLC ratio between 0.03 and 32 (n=311), with median survival of 30 versus 39 months, respectively. We incorporated abnormal FLC ratio with the International Staging System (ISS) risk factors (that is, albumin <3.5 g/dl and serum β2-microglobulin ⩾3.5 g/l), to create a risk stratification model with improved prognostic capabilities. Patients with 0, 1, 2 or 3 adverse risk factors had significantly different overall survival, with median survival times of 51, 39, 30 and 22 months, respectively (P<0.001). These findings suggest that the serum FLC ratio at initial diagnosis is an important predictor of prognosis in myeloma, and can be incorporated into the ISS for improved risk stratification.

Use of cyst fluid CEA, CA19-9, and amylase for evaluation of pancreatic lesions.

OBJECTIVES The study goals were development of reference intervals and an interpretive algorithm for pancreatic cyst fluid tumor markers. DESIGN AND METHODS 442 pancreatic cyst fluids were tested for CEA, CA19-9, and amylase. RESULTS CEA>30 ng/mL discriminates mucinous from non-mucinous cysts. After CEA analysis, amylase and CA19-9 segregate non-mucinous and mucinous subtypes, respectively. CONCLUSIONS Pancreatic cyst fluid tumor markers supplement other diagnostic measures. This study provides estimated reference intervals and an algorithm for interpretation.

Catecholamine Interference in Enzymatic Creatinine Assays

BACKGROUND Enzymatic creatinine assays are routinely used in clinical laboratories to provide more accurate estimated glomerular filtration rates and to avoid a perceived lack of analytical specificity associated with picrate (Jaffe) methods. Negative interferences with the enzymatic creatinine assay, which we noted in several patients on dopamine or dobutamine, prompted our further investigation into interference of catecholamines with enzymatic methods. METHODS Spiked solutions of dopamine, dobutamine, epinephrine, and norepinephrine were added to pooled sera at catecholamine concentrations consistent with clinically relevant dosing. Creatinine was measured enzymatically on the Roche P-Modular, Ortho Clinical Diagnostics Vitros 350, and Abbott i-STAT. Jaffe methods were performed on the Roche P-Modular and Siemens Dimension RxL. In 10 patients receiving dopamine and/or dobutamine via a venous or arterial line we evaluated and compared the extent of in vivo creatinine interference in paired serum samples obtained by venipuncture and from indwelling catheters. RESULTS All catecholamines caused significant negative interference with the Roche enzymatic creatinine assay, most pronounced for dopamine and dobutamine. The Vitros enzymatic assay demonstrated slight negative interferences, and i-STAT enzymatic and Jaffe methods were unaffected by the presence of catecholamines. Significant (P < 0.001) differences in creatinine concentrations by Roche enzymatic vs Jaffe methods were observed in venipuncture specimens compared with arterial or venous catheter specimens, suggesting dopamine and dobutamine reversibly adhere to the catheter lumen. CONCLUSIONS Negative interferences were pronounced for Roche enzymatic results in blood samples obtained from indwelling catheters, a phenomenon not observed in peripheral draws. Physicians and laboratorians should be alert to the possibility of a falsely low creatinine result and reevaluate questionable samples using a method unaffected by catecholamines.

LDLR promoter variant and exon 14 mutation on the same chromosome are associated with an unusually severe FH phenotype and treatment resistance.

Familial hypercholesterolemia (FH) is the most common form of autosomal-dominant hypercholesterolemia, and is caused by mutations in the low-density lipoprotein receptor (LDLR) gene. Heterozygous FH is characterized by elevated low-density lipoprotein (LDL) cholesterol and early-onset cardiovascular disease, whereas homozygous FH results in more severe LDL cholesterol elevation with death by 20 years of age. We present here the case of an African-American female FH patient presenting with a myocardial infarction at the age of 48, recurrent angina pectoris and numerous coronary artery stents. Her pretreated LDL cholesterol levels were more typical of a homozygous FH pattern and she was resistant to conventional lipid-lowering treatment, yet her other clinical parameters were not necessarily consistent with homozygous FH. Genetic testing revealed two LDLR variants on the same chromosome: one a novel missense mutation in exon 14 (Cys681Gly) and the other a promoter variant (IVS1-217C>T) previously shown to result in increased LDLR transcription. Disease-associated PCSK9 or APOB mutations were not identified in this individual. Overall, her genetic and clinical profile suggests that enhanced expression of the mutant LDLR allele resulted in a severe phenotype with characteristics of both heterozygous and homozygous FH.

LC-MS/MS quantitation of ribavirin in serum and identification of endogenous isobaric interferences.

BACKGROUND Ribavirin is a nucleoside analog used in treatment of chronic hepatitis C. It is associated with severe, dose-dependent toxicities, including hemolytic anemia. To facilitate therapeutic drug monitoring, a liquid chromatography-tandem mass spectrometry method was validated for quantitation of ribavirin in serum. METHODS After protein precipitation, ribavirin is quantitated using a (13)C(5)-ribavirin internal standard, on a Hypercarb analytical column designed for retention of polar analytes. RESULTS The analytical method shows excellent precision, sensitivity, and specificity. In vitro drug stability was also assessed. Interestingly, endogenous isobaric compounds were noted in both human and bovine serum; these could be chromatographically separated from the ribavirin peak. Addition of exogenous uridine and cytosine increases the size of the isobaric peaks, suggesting that these compounds are the source of the endogenous interference. CONCLUSIONS This method uses mass spectrometric transitions that have been used in other published methods, but also separates ribavirin from isobaric peaks that were not described. These peaks were determined to be endogenous nucleosides. Laboratories quantitating ribavirin in biological matrices should be aware of the potential for isobaric interferences, and take steps to chromatographically separate them from the ribavirin peak for accurate quantitation.

Management structure: establishing a laboratory utilization program and tools for utilization management.

As laboratories are challenged to do more with fewer resources, the pathologist and laboratory director will play a greater role in improving the effectiveness of the laboratory, as well as addressing the overuse, misuse and underuse of laboratory testing. We describe the necessary characteristics for pathologists and laboratory directors to successfully lead utilization efforts, as well as key leadership tools and essential steps in creating a utilization management program. When we established a laboratory test utilization program de novo, it became clear how important the laboratory director was in guiding those initiatives by working with stakeholders outside of the laboratory, particularly clinicians, nurses and administrators.

Comparison of a new serum topiramate immunoassay to fluorescence polarization immunoassay.

Topiramate is a newer anticonvulsant used to treat epilepsy, migraines, bipolar disorder, posttraumatic stress, and other conditions. Serum topiramate concentrations are measured to determine optimal levels, address therapeutic failure or drug-drug interactions, and assess compliance. Two high-throughput assays for serum topiramate measurement were compared: the Seradyn fluorescence polarization immunoassay (FPIA) on an Abbott TDx/FLx instrument and a new immunoassay from ARK Diagnostics performed on an Olympus AU680 automated analyzer. Precision, linearity, limit of quantitation, carryover, spike recovery, and endogenous interferences were found to be acceptable for the ARK assay. These studies were complemented by comparison of 120 patient samples analyzed using both methods. The ARK immunoassay performed comparably to FPIA with minimal difference in serum topiramate concentrations within the therapeutic range (2.0-20 μg/mL). A slight systematic discordance was observed at higher concentrations (greater than 30 μg/mL) with ARK immunoassay results being on average 6% higher than FPIA. Thus, the ARK immunoassay appears to provide acceptable analytical performance and comparability to FPIA; furthermore, the assay is compatible with high-throughput autoanalyzers.

Pharmacogenetics of Solid Tumors: Directed Therapy in Breast, Lung, and Colorectal Cancer: A Paper from the 2008 William Beaumont Hospital Symposium on Molecular Pathology

Genetic variability in drug-metabolizing enzymes and signaling pathways affects chemotherapy-related toxicity and treatment outcome in cancer. In breast and colorectal cancer, polymorphisms in metabolic enzymes involved in tamoxifen and irinotecan therapies has led the U.S. Food and Drug Administration to address genetic factors relevant to patient consideration of treatment with these compounds. Tamoxifen therapeutic failure in breast cancer has been associated with reduced CYP2D6 activity due to inefficient activation of tamoxifen. Irinotecan toxicity in colorectal cancer is more common in patients with reduced-activity UGT1A alleles, resulting in excessive exposure to the potent SN-38 metabolite. In colorectal and lung cancers, somatic mutations in the epidermal growth factor receptor and downstream signaling molecules have been associated with the therapeutic outcome of epidermal growth factor receptor-directed therapies. This review discusses the current knowledge regarding the utility of single gene-UGT1A1, CYP2D6, EGFR, and KRAS-or multigene analysis, for optimizing breast, colorectal, and lung cancer therapy. Current advances in these areas highlight how pharmacogenetics help personalized decision-making for patient management.

Clinical Impact of Discordance in Serum Albumin Measurements on Myeloma International Staging System

tive explanation for the limited effect of chemotherapy on prostate cancer. Admittedly, we have not considered the intriguing possibility that much of the symptomatic improvement, palliative benefit, and perhaps even some of the survival advantage could be attributed to the pulsed corticosteroids administered with docetaxel. As they correctly point out, the available trials do not allow for the dissection of relative contributions of dexamethasone and docetaxel. Though we agree with their concerns, compelling clinical observations from many studies suggest that chemotherapy does possess clinically meaningful palliative efficacy in some patients with castration-resistant prostate cancer, and the available experience with dexamethasone alone makes it unlikely, in our view, that this accounts for the observed results of the clinical trials. Nonetheless, their concerns add to our apparently shared view that there is an urgent need to reconsider the conceptual framework on which we are developing prostate cancer therapy, and certainly underscores our sense that available therapy for castration-resistant prostate cancer has yet to pass a milestone of efficacy that would justify a sense of major accomplishment on the part of medical oncologists.

Pharmacogenomics of tamoxifen and irinotecan therapies.

Genetic variability in drugmetabolizing enzymes affects the toxicity and efficacy of many compounds, including the chemotherapeutic agents irinotecan and tamoxifen. The correlation of clinical response to polymorphisms in enzymes associated with metabolism of these two drugs has led to the recommendation that patients who receive them undergo genotyping analysis. Irinotecan toxicity in patients who have colorectal cancer has been linked to reduced activity of uridine diphosphate-glucuronyltransferase 1A1 (UGT1A1). Reduced cytochrome P450 (CYP) 2D6 activity leads to therapeutic failure of tamoxifen in the prevention and treatment of breast cancer, as a result of absence of conversion of the prodrug to its active forms. This article discusses current knowledge of the usefulness of UGT1A1 and CYP2D6 genotyping in the context of cancer chemotherapy and highlights the need for additional studies to clarify the many issues remaining.