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PubMed1991

Detecting nonhemolytic Pasteurella haemolytica infections in healthy Rocky Mountain bighorn sheep (Ovis canadensis canadensis): influences of sample site and handling.

Effects of sampling procedures on ability to culture Pasteurella spp. from Rocky Mountain bighorn sheep (Ovis canadensis canadensis) were examined experimentally. Sample site influenced (P less than 0.0001) recovery of P. haemolytica in adult bighorn sheep. We isolated nonhemolytic P. haemolytica from 18 of 19 tonsillar swabs and 18 of 19 tonsillar biopsies from adult sheep, yet only four of 19 nasal swabs yielded isolates. Sample handling also affected (P less than 0.0001) recovery of P. haemolytica. Nonhemolytic P. haemolytica was cultured from 14 of 19 tonsillar swabs plated directly onto blood agar, but from only two of 19 swabs stored for 24 hr in modified Stuart's medium. We detected nonhemolytic P. haemolytica at least once in bronchial aspirates from four and in nasal swabs from three of six bighorn lambs. Based on direct cultures of tonsillar swabs and/or biopsies, all 26 bighorn sheep (seven lambs, 19 adults) sampled were infected with nonhemolytic P. haemolytica; only two lambs developed pneumonia during the study period. Thirty-four of 37 nonhemolytic P. haemolytica isolates tested were biotype T; three were biotype A. Serotypes 3; 4; 3, 4 and 3, 4, 10 were identified in a subsample of 17 isolates. Our data suggest tonsillar swabs or biopsies plated directly onto blood agar and incubated immediately offer the greatest probability of recovering nonhemolytic P. haemolytica from health bighorn sheep.

Animals↗
PubMed1984

Novel device for quantitatively collecting small volumes of urine from laboratory rats.

A reusable urinary collection device suitable for quantitative collection of uncontaminated urinary samples from rats without using a metabolism cage has been designed. The device can be attached to the pelvic skin within 5 min with minimum handling and discomfort to the unanesthetized rat using an adhesive. The suitability of this device was investigated by collecting and analyzing urine over a 48-h period following the intraperitoneal injection of [14C]inulin. A two-way crossover study was done with samples from one of the two experiments being collected while the animal was housed in a commercially available metabolism cage equipped to separate urine and feces. The percent of the dose excreted, food and water consumption, and the urinary output were not statistically different for rats housed in the metabolism cages or with the collection device attached. Histopathological examination of the rats revealed no pathology after a 24-h period except minor skin inflammation which occurred both in controls and animals to which the device was attached. These studies demonstrate the comparability of the new urine collection device to a commercially available metabolism cage in the quantitative collection of small (0-7 mL) urine samples with less contamination of the samples from the environment.

Animals↗
PubMed1992

Measuring cytokine levels in blood. Importance of anticoagulants, processing, and storage conditions.

The stability and recovery of six human recombinant cytokines (tumour necrosis factor (TNF), interferon-alpha (IFN-alpha), IFN-gamma, interleukin-1 alpha (IL-1 alpha), IL-1 beta, and IL-6) from whole blood was investigated with a view to optimizing blood collection and storage procedures prior to performing immunoassays. Blood from healthy volunteers was subjected to various processing and storage procedures. Blood samples were treated with either: ethylenediamine tetraacetic acid (EDTA) (1.5 mg/ml blood) (E); EDTA/Trasylol (1.5 mg and 1000 KIU/ml blood) (ET); heparin (30 IU/ml) (H) or allowed to clot (serum). The bloods were spiked with individual cytokines, split into aliquots and kept at 4 degrees C or RT. In the first instance spiked bloods from healthy volunteers (n = 5 per cytokine) were processed using sterile and non-pyrogenic materials and procedures. At regular time intervals, samples were cold spun, separated, flash frozen and assayed for the appropriate cytokine using RIA/IRMA methods. In a further study, timed separation was repeated with spiked blood from healthy volunteers (n = 5 per cytokine) using normal commercially available blood collection materials and procedures. In a third study, spiked blood from healthy volunteers (n = 3 per cytokine) was processed under sterile and non-pyrogenic conditions, and the blood samples separated, aliquoted and flash frozen within half hour of collection. These were then subjected to repeated cycles of freeze thawing at 4 degrees C or RT before assaying. In general, the stability of cytokines in whole blood was improved by storage at 4 degrees C and/or rapid separation. There was no significant difference between samples handled under sterile, non-pyrogenic conditions and those collected using normal blood collection procedures. The blood collection procedures described in this paper did not induce any of the six cytokines in the unspiked blood. Overall, EDTA-treated samples performed most consistently. The addition of trasylol did not significantly affect the results. Most of the cytokines appeared unaffected by up to three freeze thaw cycles. The stability and recovery of the spiked cytokines varied from least stable to most stable spiked cytokine as follows; TNF-alpha less than IL-6 less than IFN-gamma less than IL-1 alpha less than IFN-alpha less than IL-1 beta. The recovery of spiked IFN-gamma from heparinized plasma samples was considerably higher than any other plasma or serum samples. The recovery of spiked TNF-alpha and IL-6 from serum samples was consistently lower than amounts recovered from plasma samples (anticoagulant treated).(ABSTRACT TRUNCATED AT 400 WORDS)

Anticoagulants↗
PubMed1991

An association between chromosomal abnormalities in rapidly frozen 2-cell mouse embryos and the ice-forming properties of the cryoprotective solution.

This paper investigates the effect of straw handling on the viability of 2-cell mouse embryos rapidly frozen in dimethyl sulphoxide (DMSO) solutions. During the brief (3 min) equilibration step, straws were either rotated periodically to keep the embryos in suspension, or kept still to allow the embryos to settle onto the the inner surface of the straw. The effects of these straw movements were tested with cryoprotectant solutions containing 1.5, 3.0 or 4.5 M-DMSO. Rapidly cooled straws containing 4.5 M-DMSO vitrify throughout on cooling, but ice forms on warming. The survival and normality of embryos frozen in 4.5 M-DMSO was not influenced by straw handling as 91-92% formed blastocysts in vitro, 77-78% formed normal fetuses, and no chromosomal rearrangements were observed. In solutions containing less than 4.5 M-DMSO ice formation occurred throughout (1.5 M-DMSO), or in parts (3.0 M-DMSO) of the cryoprotectant during cooling. The viability of embryos frozen in 3.0 or 1.5 M-DMSO solutions was reduced both in vitro and in vivo and structural chromosome aberrations, predominantly tri- and quadri-radial rearrangements, were observed. The reduction in embryo viability, and the chromosomal damage was particularly pronounced in embryos frozen in 3.0 M-DMSO in straws which were rotated during the equilibration step (47% blastocysts, 15% fetuses, 77% chromosome rearrangements). The results indicate that rapid freezing of 2-cell mouse embryos in 4.5 M-DMSO is safe and efficient, whereas freezing at lower DMSO concentrations is associated with severe chromosome damage, and reduced viability in vitro and in vivo.

Animals↗
PubMed2005

Comparison of performance characteristics between first- and third-generation hematology systems.

In 1996, Barnes-Jewish Hospital introduced the first fully robotic hematology system in North America. This first-generation Coulter/IDS robotic automated system consisted of a series of transport lanes, inlet and outlet stations, 2 robotic arms, and an on-line slide maker/strainer. The success of the system and its exceptional performance was detailed in an article published in 1998. In 2004, our laboratory replaced this system with a new third-generation robotics system, the LH 1502 from Beckman Coulter, Inc. The new system consists of 2 LH 755 workcells (LH 750 plus slide maker/stainer), an inlet/outlet unit, and a stock-yard. The system has been interfaced to our laboratory computer system (Cerner Millieum) by customized software that allows auto-verification and testing rules to be applied to individual samples. Since its implementation in January 2005, we have monitored its performance characteristics relative to the previous first generation system. We report here on our findings through June 2005. We compared and contrasted the two systems with respects to the following parameters: (1) sample handling; (2) reduction in staff exposure to hazardous materials; (3) stat and routine turnaround times; (4) productivity; (5) reduction in backup testing; (6) operating costs; (7) payback; and (8) reduction in FTEs. We found that manual sample handling was virtually identical between the two systems. The LH 1502 holds a slight edge over our older system with respect to staff exposure mainly due to further reduction in manual backup testing. Stat TAT after introduction of the LH 1502 showed an additional 44% drop from 50 to 28 minutes, while the routine TAT was reduced by 23%, down from 61 to 47 minutes. Gains achieved in productivity after installation of the first-generation system were maintained with the LH 1502, with significant extra volume capacity yet to be utilized. The space required for operating the system was also reduced by nearly 49%. There was a 20.3% reduction in backup blood smears that required manual review (due primarily to the lower flagging rates for the LH versus STKS). The improvements in overall operating costs (> dollar 195,000) were also maintained. Payback was not considered since this was a replacement of our previous system, which had already eliminated more than 6 FTEs.

Blood Cell Count↗
PubMedDate not supplied

Sampling and storage of blood and the detection of malaria parasites by polymerase chain reaction.

Polymerase chain reaction (PCR) is now widely used in malaria research for analysis of field samples. However, little has been reported regarding loss of sensitivity due to field methodology. Therefore, studies were carried out in relation to blood sampling (anticoagulants, culture medium, filter paper), storage (temperature, time and immediate lysis) and handling (repeated thawing and freezing). The PCR was unaffected by citrate and EDTA but partly inhibited by heparin (inhibition was reversed by heparinase at optimal concentrations). Samples collected on filter paper showed a significant 100-fold lower sensitivity (compared to control samples frozen immediately after collection) when stored at 30 degrees C and 60% humidity; and the paper quality appeared to be critical. Storage of unprocessed whole blood at 4 degrees C, 20 degrees C or 30 degrees C rarely resulted in any loss of sensitivity. Repeated thawing generally resulted in 10-fold loss of sensitivity compared to blood kept frozen until DNA extraction. The presence of antimalarial drug did not apparently affect sensitivity. We conclude that the mode of collection and storage of blood samples may influence the sensitivity of detection of malaria parasites by PCR. This may be critical in studies including individuals with low parasitaemia, mixed infections and comparison of data from different settings.

Animals↗
PubMed2004

Ninhydrin treatment as a screening method for the suitability of swabs taken from contact stains for DNA analysis.

More and more swabs containing unknown traces of biological material are submitted for forensic DNA analysis. Most of the samples are swabs taken from handled items such as tools, weapons and handles etc. Therefore, we tried to develop a screening method in order to focus the investigation on samples containing biomolecules, such as amino acids which might be associated with nucleic acids. A total of 285 swabs taken from various items collected during crime scene investigations were treated with ninhydrin which leads to a purple colour for samples containing amino acids. Of the swabs 158 were classified as ninhydrin positive and 76% of these samples yielded DNA profiles that fulfil the criteria for inclusion in the German national DNA database (profile frequency greater than 1 in 100,000) or in DNA mixtures which could at least be compared with suspects. In comparison only 9% of the 127 samples shown to be ninhydrin negative, revealed a usable DNA profile. Consequently, ninhydrin treatment was found to be an effective screening method which resulted in an increase in the rate of successfully typed samples and subsequently in a reduction of the costs due to the lower number of samples that needed to be typed.

DNA Fingerprinting↗
PubMedDate not supplied

Evaluation of different procedures for processing avian air sac lavage fluid.

Air sac lavage has become a routine diagnostic tool used in pet birds; however, cytologic techniques for collection and handling of avian cells have not been reported. In this study, directed endoscopy was used to obtain the air sac washes. Different factors were compared that might affect final preservation of cell morphology, such as centrifugation speed, anticoagulant, storage temperature, time to processing, addition of glutaraldehyde to the sample, and addition of protein. The goal was to find the processing technique best suited for the evaluation of cells from air sac washes. The use of an anticoagulant did not influence cell quality. Optimal cell morphology was achieved when the sample was centrifuged at a speed of 1000 rpm (89.4 X g) and when prepared in less than an hour from the time of collection. Low temperature (5 C) tended to preserve cell quality better. The addition of protein (fetal bovine serum) helped to preserve cell quality and was of value if the sample storage time was greater than 30 min. The addition of glutaraldehyde resulted in a significant reduction in cell quality.

Air Sacs↗
PubMed2004

Restricted access materials and large particle supports for on-line sample preparation: an attractive approach for biological fluids analysis.

An analytical process generally involves four main steps: (1) sample preparation; (2) analytical separation; (3) detection; and (4) data handling. In the bioanalytical field, sample preparation is often considered as the time-limiting step. Indeed, the extraction techniques commonly used for biological matrices such as liquid-liquid extraction (LLE) and solid-phase extraction (SPE) are achieved in the off-line mode. In order to perform a high throughput analysis, efforts have been engaged in developing a faster sample purification process. Among different strategies, the introduction of special extraction sorbents, such as the restricted access media (RAM) and large particle supports (LPS), allowing the direct and repetitive injection of complex biological matrices, represents a very attractive approach. Integrated in a liquid chromatography (LC) system, these extraction supports lead to the automation, simplification and speeding up of the sample preparation process. In this paper, RAM and LPS are reviewed and particular attention is given to commercially available supports. Applications of these extraction supports, are presented in single column and column-switching configurations, for the direct analysis of compounds in various biological fluids.

Animals↗
PubMed2006

Recovering streptococci from the throat, a practical alternative to direct plating in remote tropical communities.

Throat swabs are regarded as the "gold standard" for diagnosing streptococcal pharyngitis and for surveillance research. Culturing throats in remote tropical settings is logistically difficult, and these settings are commonly burdened by high rates of streptococcal disease. The survival of streptococci on swabs may depend on whether they are of "throat" or "skin" type, as determined by emm pattern typing. The aims of this study were to compare the recovery rates of beta-hemolytic streptococci (BHS) using three different transport methods and to determine whether the recovery rates correlated with the emm pattern type. Monthly duplicate throat swabs were taken from occupants of selected households in three remote Aboriginal communities. Paired swabs were separated and handled in one of three ways: (i) direct inoculation onto culture media with cold-box transport (plated), (ii) sealed in a bag with a silica gel desiccant and cold-box transport (desiccant), and (iii) transport at ambient temperature and humidity (ambient). emm pattern typing was done by standard methods. Over 23 months, 4,842 throat swabs were taken, and 4,122 were paired. BHS were recovered on 11.5% of the 4,842 occasions (group A, 4.5%; group C, 1.7%; group G, 5.4%). Results from paired swabs showed the plated method was superior to desiccant and desiccant was better than ambient. Pooled data indicated that plated and desiccant were equivalent, and both were significantly better than ambient. There was no correlation between the emm pattern type and recovery of group A streptococci by different methods. In tropical and remote settings, cold-box transport with desiccant and subsequent inoculation of culture plates in the laboratory is a practical alternative to direct plating.

Bacteriological Techniques↗
PubMedDate not supplied

Bioreactor design for successive culture of anchorage-dependent cells operated in an automated manner.

A novel bioreactor system was designed to perform a series of batchwise cultures of anchorage-dependent cells by means of automated operations of medium change and passage for cell transfer. The experimental data on contamination frequency ensured the biological cleanliness in the bioreactor system, which facilitated the operations in a closed environment, as compared with that in flask culture system with manual handlings. In addition, the tools for growth prediction (based on growth kinetics) and real-time growth monitoring by measurement of medium components (based on small-volume analyzing machinery) were installed into the bioreactor system to schedule the operations of medium change and passage and to confirm that culture proceeds as scheduled, respectively. The successive culture of anchorage-dependent cells was conducted with the bioreactor running in an automated way. The automated bioreactor gave a successful culture performance with fair accordance to preset scheduling based on the information in the latest subculture, realizing 79- fold cell expansion for 169 h. In addition, the correlation factor between experimental data and scheduled values through the bioreactor performance was 0.998. It was concluded that the proposed bioreactor with the integration of the prediction and monitoring tools could offer a feasible system for the manufacturing process of cultured tissue products.

Algorithms↗
PubMed2004

Impact of pre-analytical handling on bone marrow mRNA gene expression.

Large clinical trials on leukaemia, require the transport of bone marrow (BM) from participating clinics to central diagnostic laboratories. We have investigated the impact of RNA extraction protocols and time delays between sample aspiration and RNA extraction on RNA quality and gene expression profiles. Intact RNA can be extracted from BM samples stored at room temperature for up to 48 h. Gene expression analyses using Affymetrix U95Av2 GeneChips and a custom-designed cDNA array in parallel showed that even short-term storage of BM has dramatic effects on mRNA expression of individual transcripts. Many probe sets/genes showed either reproducible deregulation (18.8%, analysis of variance <0.05), or inconsistent expression that differed from patient to patient (38.4%). Moderate alterations were observed in 42.8% genes, with a maximum fold change <2.0 in all experiments and at all time points. These profound effects complicate the use of unstabilized, shipped BM samples for gene expression analyses. The comparison of a variety of RNA stabilization reagents (e.g. PAXgene) resulted in partial conservation of the mRNA expression patterns. Immediate density centrifugation or erythrocyte lysis and freezing at -80 degrees C represent simple procedures that reliably preserved mRNA gene expression patterns in BM.

Bone Marrow↗
PubMed2006

Situation analysis of TB microscopy centres in Ghana.

SETTING: Public health laboratories in Ghana performing tuberculosis (TB) microscopy. OBJECTIVE: To assess the situation of the laboratories in terms of staff strength, technical skills, documentation, biosafety practices, equipment, supplies and disposal systems. DESIGN: Methods used for data collection were interviews using a structured questionnaire, informal observation of laboratory registers, disposal systems and safety measures for sputum handling. RESULTS: Of 114 laboratories visited between 2000 and 2001, 102 (89.5%) were performing TB microscopy. Of the staff working in the laboratories, 9% were medical technologists, 24% laboratory technicians, 37% laboratory assistants and 30% orderlies. Average false-negative and -positive rates were respectively 13% and 14%. Although most of the centres (85.3%) were using the recommended TB laboratory register for recording, in most cases they were not filled in accurately or completely. The majority of the available microscopes had mechanical or optical faults. Availability of other materials for smear preparation and staining ranged from 44% to 82%. The main methods employed for disposal of laboratory waste were burning and burying, but conditions were poor in most of the facilities visited. CONCLUSION: Training of laboratory personnel in TB microscopy and establishment of a quality assurance system are needed in Ghana.

Bacteriological Techniques↗
PubMed1986

Measurement of fibronectin in human body fluids.

Two facts must be taken into consideration when quantifying fibronectin in biological samples: the sensitivity of the assay method and the appropriate handling of samples. A three-antibody, non-competitive ELISA was used in the present study. This procedure offers a simple, inexpensive and very sensitive technique for evaluating fibronectin: reproducible standard curves in the range 5-100 micrograms/l, 3% variability in the assay, and a detection limit of 0.5 ng/well that allows accurate measurement of fibronectin in segmental bronchoalveolar lavage and in ascites liquid samples. Typical dilution ranged from 1/10000 for plasma to 1/100 for bronchoalveolar lavages. For long-term storage of samples two procedures are recommended. First, a rapid freezing with liquid nitrogen, storage at -20 degrees C and thawing once at 37 degrees C avoiding refreezing. Losses of immunoreactive fibronectin after 35 days storage were 15, 15 and 22% in plasma, bronchoalveolar lavages and ascites fluid, respectively. Alternatively, samples can be stored as ammonium sulphate precipitates. This allows the easy availability of the samples when assays have to be repeated, and avoids fractionation in vials and freeze-thawing cycles. Using this storage procedure, losses are, however, slightly higher (22, 25, 25%, respectively, after 35 days).

Enzyme-Linked Immunosorbent Assay↗
PubMed1980

Factors affecting the differential counting of human lymphocyte subpopulations in blood smears.

We have previously used the antibody-mediated binding of bacteria to identify Ig-bearing cells and the natural binding of bacteria to identify several lymphocyte subpopulations. By using bacteria this identification can be carried out in conventional blood smears since bacteria are small and easily distinguished from all blood elements. To develop a standardized method for identification of lymphocyte subpopulations that may become useful in clinical laboratories, we investigated here several parameters that might affect the safety and accuracy of the test, and that might simplify the procedure. We found that: (1) the rosettes formed between bacteria and lymphocytes cannot be disrupted by vigorous handling; (2) the ability fo form rosettes is a stable property of the bacterial strains; (3) for optimal results the blood sample must not be stored for more than 4 hr at 25 degrees C and the entire procedure must be performed in medium supplemented with 6% bovine serum albumin; (4) a large excess of anti-Ig antibody is required for the optimal coating of bacteria to detect Ig-bearing cells; (5) both the antibody-coated bacteria and formaldehyde-fixed bacteria can be stored at 4 degrees C or at -20 degrees C for at least 6 months; (6) the buffy coat from the blood sample can be used instead of the whole blood to reduce the time required for reading the smears; and (7) some of the pathogenic bacteria can be killed by autoclaving without modifying their binding properties. A complete and simple method which uses the bacterial adherence for the identification of lymphocyte subpopulations in blood smears is presented.

Antibodies, Anti-Idiotypic↗
PubMedDate not supplied

Performance of monolayered cervical smears in a gynecology outpatient setting in Kuwait.

OBJECTIVE: To compare ThinPrep (TP) Papanicolaou smears (Cytyc Corp., Box-borough, Massachusetts, U.S.A.) with matching conventional Papanicolaou (CP) smears for specimen adequacy, cytologic quality, diagnostic accuracy and screening time. STUDY DESIGN: In this prospective study of 1,024 women a split-sample, matched-pair design in favor of CP slides based on single-blind criteria was followed with a smear on a glass slide for CP and the remaining material collected in Preserv-Cyt solution (Cytyc) for a TP smear. A Cytobrush (Medscand, Hollywood, Florida, U.S.A.) was used for smear preparation for CP. TP smears were processed in ThinPrep 2000 (Cytyc). Smears were stained with Papanicolaou stain and were interpreted according to the Bethesda system. RESULTS: The number of satisfactory but limited (SBL) cases with TP were 77 (7.5%) as compared to 127 (12.4%) with the CP method. This reduction in SBL smears with the TP method and consequent increase in satisfactory smears were highly significant (P < .001) by McNemar's test. As regards unsatisfactory smears in discordant pairs, although the number of unsatisfactory smears was higher with TP (41 cases) as against CP (27 cases), the difference was not statistically significant (P < .05). The split-sample method showed a high correlation between the CP and TP diagnoses. TP smears had a significant advantage over CP smears in the reduction in the number of ASCUS and AGUS cases (14 vs. 29) (P < .05) and increased the pickup rate of LSIL, 6 vs. 1. Time taken to screen the TP smears was half that of CP smears. No cases of LSIL or HSIL were missed on TP smears. CONCLUSION: The liquid-based processor significantly improved the adequacy and quality of smears, resulting in fewer recall cases for SBL smears, leading to more definitive diagnoses in atypical cases, increasing the pickup rate of LSILs and reducing the screening time. A machine handling multiple specimens automatically would decrease cost and be an asset to a cytopathology laboratory.

Adolescent↗
PubMed1976

Some factors affecting the measurement of blood inorganic phosphorus in cattle.

Sixty cows were studied over 3 days, to determine the effect of site of sampling, handling stress and the tranquilliser xylazine hydrochloride, on blood inorganic phosphorus (P). Jugular venous and coccygeal mixed arterial and venous blood were compared. Saliva was also analysed for P. Buffered and unbuffered trichloracetic acid (TCA) were compared as deproteinising agents. Tail blood P was consistently 12% (range 7-17%) higher than that from the jugular vein (P less than 0.01). This difference decreased when jugular blood was sampled first but increased following administration of the tranquilliser. The drug significantly (P less than 0.01) increased the concentration of P in the saliva on 2 out of 3 days. The possible role of salivary P in affecting jugular P values, is discussed. The buffered TCA analyses gave consistently lower P readings than the unbuffered analyses. The magnitude of this effect was time dependent, being greater when the samples were left for 4 days (P less than 0.05) than when analysed the next day. There was a very strong correlation between plasma and whole blood P. It was concluded that the tissue of choice in phosphorus studies is tail blood (plasma or serum) treated with buffered TCA.

Animals↗
PubMedDate not supplied

Collection and handling of clinical blood samples to assure the accurate measurement of cocaine concentration.

The measurement of serum cocaine concentration is difficult because it is rapidly metabolized in vivo and in vitro. Previous investigators have used sodium fluoride (0.5-3.0%) in an attempt to stabilize its concentration in samples of whole blood, but these concentrations of sodium fluoride are not readily available outside the analytical laboratory. This study was performed to assess the stability of cocaine in whole blood when stabilized in a commonly available concentration of sodium fluoride (0.25%), with or without concomitant refrigeration. Whole blood was enriched with cocaine to a final concentration of 900 ng/mL and added to flasks containing sodium fluoride (0, 0.25, 0.5, and 1.0%) or 0.25% sodium fluoride plus potassium oxalate (gray-top Vacutainer tubes), after which it was stored at 4 degrees C or at room temperature. Whole blood cocaine concentrations were measured at 0, 24, and 48 h by gas chromatography. Sodium fluoride at all concentrations, with or without refrigeration and potassium oxalate, effectively inhibited cocaine degradation, with 86-91% of the drug present after 48 h. In contrast, substantial degradation of cocaine occurred in the samples stored without sodium fluoride, regardless of temperature. Thus, the use of commercial gray-top Vacutainer tubes effectively stabilizes cocaine in blood during procurement, transport, and short-term storage.

Chromatography, Gas↗