Acceptability of Lymphazurin-Contaminated Blood Samples for Preoperative Laboratory Testing
By Aida Narvios, Musa Mbahi, Caimiao Wei and Benjamin Lichtiger
Copyright 1993-2010 The University of Texas MD Anderson Cancer Center, Houston, Texas. All rights reserved.
Identification of axillary sentinel nodes is considered important in staging cancer and provides guidance in selecting optimal adjuvant therapy for this disease. These lymph nodes are the first to which lymphatic drainage from and metastasis of breast cancer occurs (1-5). Currently, two axillary sentinel node-identification techniques are used in the United States: administration of the radiocolloid technetium 99m sulfur colloid and staining with the blue dye isosulfan blue (Lymphazurin; United States Surgical, Norwalk, CT) (6). Contraindications for these techniques include allergies to technetium 99m sulfur colloid or Lymphazurin, pregnancy, prior axillary procedures, recent reduction mammaplasty, and the presence of multicentric cancers (7).
Lymphazurin is an aniline dye (2, 5-disulfonated isomer of patent blue dye) used as a contrast agent to delineate lymphatic vessels via subcutaneous injection. The chemical name for Lymphazurin is N-[4-[[4-(diethyl-amino)phenyl](2,4-disulfophenyl)methylene]-2,5-cyclohexadien-1-ylidene]-N-ethylethanaminium inner salt, sodium salt. This dye contains no preservatives. Also, it has no known pharmacologic actions. The dye is injected intradermally or intraparenchymally and subsequently picked up by the lymphatic vessels draining in the area (8). However, blue discoloration of blood samples is a concern when using Lymphazurin, especially when such discolored blood samples are the only samples available for laboratory testing. The commission on laboratory accreditation of the College of Pathologists has required laboratories to have a documented system of monitoring the quality of blood samples (9).
In our institution, 654 consecutive patients underwent sentinel lymphadenectomy for breast cancer from December 2001 to January 2003, 448 (68.5%) of whom received Lymphazurin (10). Currently, our service can perform ABO/Rh typing and antibody screening of blood samples using a traditional manual tube method and an automated solid-phase method (Immucor, Inc., Norcross, GA) (11, 12). If we experience any problems with the automated method, we further test the samples using the traditional method. Plasma collected from blood samples after injection of this dye are discolored light blue or emerald green, whereas normal plasma is amber to light yellow in color. This unusual discoloration often leads to rejection of samples by laboratories as being unsuitable for testing, as whether the dye affects the ability to correctly perform laboratory testing of blood samples is unclear. Thus, we performed the present study to evaluate blood samples submitted for ABO/Rh testing and antibody screening to compare the accuracy of the results for Lymphazurin-contaminated samples with that for uncontaminated samples.
Patients and Methods
Seventeen consecutive patients with breast cancer who consented to participate in the study were included. Approximately 10 ml of blood was drawn from each patient and stored in purple-topped tubes before and after a surgical procedure in which Lymphazurin was used. This study was approved by The University of Texas MD Anderson Cancer Center Institutional Review Board.
ABO/Rh typing and antibody screening of the samples drawn before injection of Lymphazurin were considered the “correct” results. Matching of the typing and screening results for the samples obtained after injection of the dye with those for the samples taken before injection was desired. The matching rates and corresponding 95% confidence intervals (CIs) for the manual tube and solid-phase methods were calculated based on binomial distribution using the StatXact 4 software program for Microsoft Windows (Cytel Inc., Cambridge, MA).
We performed the traditional and automated methods in parallel according to standard operating procedures for ABO/Rh typing and antibody screening of the blood samples. All 17 pairs of samples were evaluable for manual ABO/Rh typing and for both manual and automated antibody screening; only 16 pairs were evaluable for automated ABO/Rh typing. The ABO/Rh typing results for the samples drawn before the dye injection perfectly matched those for the samples obtained after the injection using both the traditional and automated method, with 95% CIs of 0.805-1.000 and 0.794-1.000, respectively. The results of antibody screening using the manual method also matched perfectly (95% CI, 0.805-1.000). We observed one incorrect antibody-screening result among the 17 samples using the automated method.
The accurate ABO/Rh typing and antibody screening results for blood samples contaminated with Lymphazurin were comparable with those for uncontaminated blood samples. This is significant, because localization of the sentinel lymph nodes as part of the management of breast, cervical, and colon cancer is popular. It also has become a powerful prognostic indicator for recurrence and survival in patients with primary melanoma (13-15). Diagnostic tests may not be limited to ABO/Rh typing and antibody screening but may also include tests that use plasma or serum samples. Technologists and pathologists should familiarize themselves with such changes in blood-sample color so that they will be able to handle samples appropriately. We initiated this study as a proactive initiative in our laboratory to provide blood samples in a timely manner after administration of Lymphazurin when blood samples not contaminated with the dye are unavailable. We used standard operating procedures for both manual and automated ABO/Rh typing and antibody screening for the contaminated and uncontaminated blood samples.
We did not observe that Lymphazurin chemically interfered with the reagents we used for ABO/Rh typing and antibody screening testing. The consistency and comparability of the typing and screening results confirmed this lack of interference. However, our sample size was limited.
Sentinel lymph node identification has become popular in the management of malignancies for prognostic assessment. Thus, accurate visualization of lymph nodes is imperative. Blood samples contaminated with Lymphazurin are acceptable for ABO/Rh typing and antibody screening when no other blood samples are available. More studies are needed to determine the effect of this dye in other diagnostic blood tests.
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