血浆同型半胱氨酸及其相关硫醇物在全血中的稳定性研究

目的 观察含EDTA的全血样本放置时间、保存温度以及不同稳定剂对血浆同型半胱氨酸(homocysteine,Hcy)及其相关硫醇物水平的影响.方法 用含EDTA、EDTA-氟化钠(EDTA-NaF)、EDTA-3-Deazaadenosine(EDTA-3DA)的试管收集17名健康成人静脉血,置于碎冰上(0～4 ℃)或室温中(25 ℃)保存,放置0、3、6、24、48 h后分离血浆.用HPLC法测定血浆总同型半胱氨酸(tHcy)、总半胱氨酸(total cysteine,tCys)、总半胱氨酰甘氨酸(total cysteinylglycine,tCysGly)、总谷胱甘肽(total glutathione,tGSH)浓度.设定全血样本0 h分离血浆所测硫醇物浓度为基础值.结果 EDTA管在室温中放置3、6、24、48 h,tHcy分别增加38.5%、64.2%、141.9%、225.4%;tCysGly、tGSH在3 h分别增加20.0%、37.9%,tCys则降低3.5%.EDTA管在碎冰上保存,各硫醇物浓度6 h内增加不超过5%.EDTA-3DA和EDTA-NaF管在室温放置3 h,与各自基础值相比,血浆tHcy、tCys、tCysGly、tGSH浓度差异无统计学意义(EDTA-3DA管:F值分别为0.01、0.94、0.09、0.01,P值均>0.05;EDTA-NaF管:F值分别为0.85、0.04、0.03、0.02,P值均>0.05).结论 EDTA抗凝血浆,所测tHcy及其相关硫醇物浓度呈时间、温度依赖性增加.血浆tHcy等硫醇物测定的分析前处理条件必须标准化.EDTA-3DA和EDTA-NaF管可使血浆tHcy、tCys、tCysGly、tGSH在室温中至少稳定3 h.

Abstract：

Objective To investigate the effects of different stabilizers, time and temperature before centrifugation on the stability of homocysteine (Hcy) and other related thiols levels involving EDTA-containing whole blood.Methods Blood was drawn from 17 healthy adults and collected into tubes containing EDTA, EDTA plus NaF and EDTA plus 3-deazaadenosine(3DA),then stored on crush ice(0-4 ℃) immediately or at room temperature(25 ℃).Plasma was separated at 0, 3, 6, 24 and 48 hours, respectively.The levels of plasma total Hcy (tHcy), total cysteine (tCys), tatal cysteinylglycine (tCysGly) and tatal glutathione (tGSH) were measured by HPLC.The plasma immediately separated was used as baseline sample. Results In EDTA tubes stored at room temperature, tHcy levels increased by 38.5%, 64.2%, 141.9%, 225.4% for 3, 6, 24, and 48 h, respectively.The levels of tCysGly and tGSH increased by 20.0% and 37.9% within 3 h, however, tCys decreased by 3.5%.The levels of the thiols increase by less than 5% up to 6 h in EDTA tubes stored on crush ice.In EDTA-3DA and EDTA-NaF tubes, no statistical differences were observed in the plasma levels of tHcy, tCys,tCysGly and tGSH compared with their respective baseline values at room temperature for 3 h(EDTA-3DA tubes:F=0.01,0.94,0.09,0.01,all P>0.05;EDTA-NaF tubes:F=0.85,0.04,0.03,0.02,all P>0.05).Conclusions The EDTA-plasma levels of tHcy and other related thiols are time and temperature-dependent. There is a strong need for standardization of blood sample collection and processing in tHcy and other thiols assays. The plasma concentrations of tHcy, tCys, tCysGly and tGSH were stable for 3 h at least in the EDTA-3DA and EDTA-NaF tubes kept at room temperature.     

Whole blood samples for adrenocorticotrophic hormone measurement can be stored at room temperature for 4 hours

Introduction: The aim of this study was to investigate and compare the stability of adrenocorticotrophic hormone (ACTH) in whole blood stored on ice and at room temperature for up to 48?hours. This study differs from previous studies by a larger data material.

Materials and methods: EDTA-blood samples from 30 patients were collected, aliquoted and stored on ice or at room temperature for 0, 2, 4, 24, or 48?h before centrifugation, and the plasma was stored frozen until analysis. All samples were analyzed using an automated electrochemiluminescence immunoassay on cobas 6000 e601. The change in ACTH concentration was illustrated as ACTH recovery compared to standard conditions defined as samples stored immediately on ice, centrifuged and plasma frozen within 1?h. A change in ACTH concentration of more than 10% was considered to be of clinical relevance.

Results: The results showed no clinically relevant change in ACTH recovery for up to 4?h compared to standard conditions. For samples stored at room temperature for 4?h, a significant (p?Conclusion: The comparison between samples stored at room temperature for up to 4?h and standard conditions showed that ACTH samples do not require cooling until centrifugation, if a mean difference in ACTH concentration of ?4.3%, between the individual results, can be accepted.     

Multicenter evaluation of the Roche NT-proBNP assay and comparison to the Biosite Triage BNP assay

BACKGROUND: Brain natriuretic peptides (BNPs) are useful in the assessment of heart failure, left ventricular dysfunction, and acute coronary syndromes. METHODS: We performed a multicenter evaluation of the automated Roche NT-proBNP assay and compared its performance to the Biosite Triage BNP assay. RESULTS: The N-terminal (1-76) pro brain natriuretic peptide (NT-proBNP) method is precise (CV2-fold higher CV, and plasma samples are more labile when stored at room temperature and 4 degrees C. Comparison studies showed a reasonable correlation between NT-proBNP and BNP assays, with a substantially higher slope bias of 6-20 for the NT-proBNP assay. CONCLUSIONS: The automated Roche NT-proBNP assay has good analytical performance and better precision than the Biosite BNP assay. Unlike BNP, NT-proBNP is stable in EDTA plasma for 3 days at room temperature or longer at 4 degrees C. The Roche NT-proBNP is fully automated and will accommodate the testing of large numbers of clinical samples for assessing cardiac dysfunction.     

Stability of 5-fluorouracil in whole blood and plasma

We studied the stability of 5-fluorouracil (5-FU) in plasma and whole blood kept at room temperature and on ice for 1 to 24 h. At room temperature, there was a steady loss of 94% of the parent drug over 24 h in whole blood and 52% in plasma. In the presence of an excess of uracil, 5-FU was stable for 24 h, suggesting that the loss of 5-FU is the result of enzymatic degradation. 5-FU is more stable in whole blood and plasma when samples are kept cold. For blood and plasma samples maintained on ice, the loss was only 30% and 10% of the parent drug in the respective samples over 24 h. Frozen plasma samples (-20 degrees C) were stable for five weeks. Blood specimens collected for quantifying 5-FU should be immediately placed on ice, and the plasma should be separated and frozen as promptly as possible.     

Prevention of in vitro lipolysis by tetrahydrolipstatin

BACKGROUND: Metabolic effects of free fatty acids (FFAs) frequently are tested using combined infusion of triglycerides and heparin, which stimulates lipolysis in vivo. Ongoing in vitro lipolysis, however, probably produces falsely high plasma FFA concentrations under these conditions. Therefore, this study aims to assess the efficacy of tetrahydrolipstatin (THL) in inhibiting plasma lipolytic activity and to improve plasma FFA determination. METHODS: Plasma concentrations of FFAs and glycerol were measured in five healthy subjects in the presence and absence of THL. Blood was drawn at baseline, during infusion of a triglyceride emulsion (1.5 mL/min), and during infusion of triglycerides plus heparin (0.2 IU. kg(-1). min(-1)). In addition, the effects of storage temperature of the samples were analyzed. RESULTS: In samples frozen immediately after collection, plasma FFAs were 28% lower in the presence of THL than in its absence (P = 0.008). When THL-free plasma was incubated for 3 h on ice or at room temperature, plasma FFAs were 22% (P = 0.02) and 91% (P = 0.0004) higher, respectively, than in samples frozen immediately. The addition of THL blunted temperature-dependent in vitro lipolysis by 88% (P<0.01) and 89% (P <0.001) after incubation on ice and at room temperature, respectively. Changes in plasma glycerol concentrations exhibited similar behavior. CONCLUSIONS: THL, which is safe and easy to handle, is a potent inhibitor of in vitro lipolysis and could, therefore, be added to blood samples drawn during triglyceride/heparin infusions to allow more accurate determination of plasma FFA concentrations.     

检测前因素对N末端B型尿钠肽原测定值影响分析

目的 分析运动、容器材质、抗凝剂种类、存放条件等检测前因素对N末端B型尿钠肽原(N terminal-pro-b-type natriuretic peptide,NT-proBNP)检测结果的影响。 方法 采用电化学发光法,分别检测不同材质容器、不同种类抗凝剂和不同存放条件下74例心衰患者和70名健康人血液中NT-proBNP水平,以及70名健康人运动前、后的NT-proBNP水平。 结果 行走20 min后健康组NT-proBNP浓度较安静状态升高10%~20%,差异有统计学意义。玻璃促凝管和塑料促凝管两种不同材料的容器对NT-proBNP检测值无影响。EDTA抗凝血浆的NT-proBNP检测值较肝素锂抗凝血浆与促凝血清低,差异有统计学意义。肝素锂抗凝血浆与促凝血清的结果差异无统计学意义。常温加盖存放3 d或反复冻融3次均不影响NT-proBNP检测结果。 结论 NT-proBNP检测对存放条件要求不高,但运动和抗凝剂的选用会影响NT-proBNP的水平,临床检测时应加以标化,避免检测结果的波动。     

Influence of the sample matrix on the stability of beta-CTX at room temperature for 24 and 48 hours

The measurement of beta-C-telopeptides of type I collagen (beta-CTX) reflects the rate of bone resorption in a variety of metabolic bone disorders and it is increasingly used to assist diagnosis and follow-up of these pathologies. Since preanalytical biases in the results of this marker can decrease its clinical usefulness, specific stability studies should be developed to prevent that inconsistent results of laboratory testing might affect patient health and waste economical resources. Three blood samples were simultaneously collected without venous stasis into evacuated tubes containing no additives, K2 EDTA or lithium heparin, from 23 out-patients referred to our phlebotomy service for routine laboratory testing. After centrifugation and separation of the specimens, a first aliquot was immediately analyzed, whereas a second and third aliquot was processed after a 24- and 48-hour storage at room temperature (21 degrees C). Beta-CTX was assayed on the automated electrochemiluminescence analyzer E170. A modest and clinically irrelevant underestimation was observed in lithium heparin plasma when compared with either K2 EDTA (-7.1%; 95% C.I. -2.0 to -12.3%; p < 0.001) or serum (-7.8%; 95% C.I. -3.2 to -12.4%; p < 0.001), but not between serum and K2 EDTA (+0.8%, 95% C.I. -5.3 to +6.9%; p = 0.260). Storage at room temperature in K2 EDTA plasma introduced a modest and clinically negligible decay in immunoreactivity (-4.4% and -5.7% at 24 and 48 hours, respectively), whereas storage at room temperature in both serum (-17.6% and -28.6% at 24 and 48 hours, respectively) and lithium heparin plasma (-29.1% and -44.0% at 24 and 48 hours, respectively) was associated with a substantial decay and a larger inter-individual variability in the measurable concentration of the analyte. In conclusion, the results of our investigation demonstrate that EDTA plasma is the most suitable sample matrix for the storage of beta-CTX at room temperature after centrifugation.     

Effects of storage and handling conditions on concentrations of individual carotenoids, retinol, and tocopherol in plasma

We investigated the effects of storage and handling on measured values for carotenoids, retinol, and tocopherol in plasma. We found no significant differences in the concentrations of these analytes measured in plasma samples that were frozen immediately after separation as compared with replicate samples maintained at room temperature in the dark for 24 h. Analytes were stable in solvents for at least 18 h at 23 degrees C after extraction. Purging samples with nitrogen gas before freezing had no detectable beneficial effects. All analytes were stable in plasma stored at -70 degrees C for at least 28 months or at -20 degrees C for five months. By 15 months the concentrations of carotenoids were significantly less (P less than 0.05) in plasma stored at -20 degrees C than in plasma stored at -70 degrees C, while retinol and tocopherol concentrations were not significantly different. Concomitant with the decrease in carotenoids was the appearance of unidentified peaks in the ultraviolet. Adding ascorbic acid or butylated hydroxytoluene antioxidants to the precipitating solvent did not alter the losses of carotenoids or alter the appearance of unidentified peaks. Under appropriate conditions, plasma carotenoids, retinol, and tocopherol are stable for more than two years.     

Stability of cyclophosphamide and mesna admixtures in polyethylene infusion bags

BACKGROUND: Cyclophosphamide (CYP) is used to treat cancers in combination with mesna to prevent cystitis. The use of extemporaneously prepared admixtures of these drugs must be supported by documentation of their chemical stability.OBJECTIVE: To evaluate the chemical stability of CYP and mesna admixtures in dextrose 5% polyethylene infusion bags.METHODS: The drugs were diluted in 100-mL dextrose 5% infusion bags to final concentrations of CYP 10.8 mg/mL with mesna 3.2 mg/mL (solution A) and CYP 1.8 mg/mL with mesna 0.54 mg/mL (solution B). Six infusion bags from each solution were stored at 4 degrees C and 6 were stored at room temperature. Triplicate HPLC determinations were performed on each bag to measure drug concentrations at 0, 1, 2, 4, 6, 12, 24, 48, and 96 hours.RESULTS: At 96 hours, drug concentrations in all solutions stored at room temperature were found to be <80% compared with the initial concentrations. The solutions stored at 4 degrees C retained at least 90% of the initial drug concentrations at 48 hours. The pH of solutions A and B stored at room temperature decreased significantly by 4.44 and 4.31 units, respectively. The pH of the refrigerated infusion bags decreased significantly by 1.46 units for solution B.CONCLUSIONS: Admixtures stored at 4 degrees C (pH 7.90 +/- 0.004; mean +/- SD) are stable for 48 hours. The CYP and mesna combination can be infused at room temperature over 6 hours without significant degradation of the drugs. Stabilities are dependent on pH, temperature, and/or concentration.     

Preanalytical factors affecting the stability of matrix metalloproteinase-2 concentrations in cerebrospinal fluid

BACKGROUND: Matrix metalloproteinases (MMPs) are crucially involved in central nervous system inflammation. This study assesses preanalytical factors on MMP-2 concentrations in cerebrospinal fluid (CSF). METHODS: The concentrations of MMP-2 in CSF obtained from 13 patients were measured using ELISA. Identical measurements were done from the samples of the CSF from the same collection that were successively stored in glass tubes, stored at room temperature (21 degrees C), or refrigerated (4 degrees C) and frozen and thawed five times. RESULTS: After 48 h of storage at room temperature and refrigeration, there was a significant decrease in the concentrations of MMP. Sample storage in polypropylene or glass tubes led to a comparable decrease in MMP-2 concentrations. The freeze-thaw cycles, which were repeated five times, did not significantly affect MMP-2 concentrations. CONCLUSIONS: The storage of CSF at room temperature or refrigeration significantly decreases MMP-2 concentrations. Subsequent freeze-thaw cycles or glass tube material did not influence MMP-2 concentrations. Samples of CSF should be frozen immediately after collection to ensure accuracy of MMP measurements.     

Interference and blood sample preparation for a pyruvate enzymatic assay

BACKGROUND: To assess the severity of circulatory failure, a pyruvate enzymatic assay was performed on whole blood using lactate dehydrogenase to catalyze the conversion of pyruvate to lactate. We investigated factors related to blood sample collection and preparation that might influence the results, including the timing of blood deproteinization, temperature of sample storage, and hemolysis. METHOD: A total of 25 whole blood specimens were collected for this study. Each sample was divided into 2 parts: one stored at room temperature (RT) and another kept on ice. The samples were deproteinizied by using 8% perchloric acid (PCA) at varying times after collection; the first deproteinization was immediately after the blood was drawn (0 h), then at 1 h intervals for 6 h and also in samples kept overnight. The supernatant samples were analyzed soon after deproteinization using a COBAS Centrifugal Analyzer. In another set of samples, the blood was immediately deproteinized, and the supernatants were stored at RT and 4 degrees C and assayed for pyruvate at varying times, as above. Finally, the effect of hemolysis on the blood pyruvate enzymatic assay was also evaluated. RESULTS: When samples were stored at RT, pyruvate levels remained constant until the third h after deproteinization, when there was an approximately 13.3% increase in pyruvate concentration. When whole blood samples were kept at 4 degrees C before deproteinization, pyruvate levels were significantly reduced over time, ranging from 37.8% to 62.2% (paired t test showed a significant mean difference, P < 0.001). No significant differences in pyruvate concentration were observed in supernatant stored at either RT or 4 degrees C. Hemolysis caused a 33.7% increase in the pyruvate concentration, equivalent to 0.18 mg pyruvate per gram per deciliter of hemoglobin. CONCLUSIONS: For a pyruvate enzymatic assay, keeping a whole blood sample at RT will not cause a significant difference in the pyruvate level as long as the sample is immediately deproteinized. Whole blood samples should not be stored in an ice bath for transport, nor should hemolyzed samples be used for a blood pyruvate enzymatic assay.     

存放时间和温度对凝血功能指标检测结果的影响

目的 探讨标本放置时间和温度对凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)、凝血酶时间(TT)、纤维蛋白原(FⅠB)等凝血指标检测结果的影响.方法 选取抗凝静脉血标本50例,血浆用于立即测定凝血4项指标和在室温放置2 h、4 h、6 h和24 h后测定凝血4项指标;并分别于室温、-4 ℃和-20 ℃下保存24 h后测定凝血4项指标.抗凝血室温放置2 h,离心分离血浆后即刻进行凝血指标检测.采用血液凝固仪测定研究指标,采用随机单位组设计资料方差分析比较各组间差异.结果 与留取即刻检测相比,血浆放置2 h APTT、PT、TT和FⅠB等各种指标水平均无明显差异;血浆标本放置4 h开始,APTT、PT和TT等指标出现明显延长,且变化程度随放置时间延长加重,FⅠB水平无明显改变;抗凝血标本放置2 h留取的血浆标本各指标均有明显变化.-4 ℃下血浆标本保存24 h APTT、PT、TT和FⅠB等指标测定结果未出现明显改变,-20 ℃下24 h APTT出现明显延长.结论 对于凝血功能4项指标的测定,采集标本后应及时送检和尽快分离血浆.常温下血浆标本应在2 h内完成测定;-4 ℃下血浆标本保存24 h PT、APTT、TT和FⅠB等指标测定结果未受影响,低温保存应注意避免标本冻融过程.     

Long-term stability of endogenous B-type natriuretic peptide (BNP) and amino terminal proBNP (NT-proBNP) in frozen plasma samples.

The aim of the present study was to assess the long-term stability of endogenous B-type natriuretic peptide (BNP) and amino terminal proBNP (NT-proBNP) in plasma samples stored at -20 degrees C without addition of protease inhibitors (e.g., aprotinin). Stability of BNP and NT-proBNP was tested in 60 EDTA plasma samples with BNP values between 30 and 420 pg/ml. Initial BNP and NT-proBNP plasma concentrations were determined within four hours after blood collection using the AxSYM BNP and the Elecsys NT-proBNP assays. Subsequently, all samples were stored at -20 degrees C and were thawed for the second BNP and NT-proBNP determination on the two instruments after one day, 30 days, 60 days, 90 days and 120 days, respectively. Mean recovery (i.e., residual immunoreactivity) of BNP and NT-proBNP expressed in percent of the initial value for the given time interval of storage was calculated. Mean recovery of BNP was less than 70% after one day of storage at -20 degrees C and decreased to less than 50% after two to four months of storage (e.g., recovery of endogenous BNP after three months of storage at -20 degrees C ranging from 0% to 71%). In contrast, mean recovery of NT-proBNP was generally greater than 90%, irrespective of the duration of storage at -20 degrees C (e.g., recovery of endogenous NT-proBNP after three months of storage at -20 degrees C ranging from 91% to 112%). In conclusion, the determination of endogenous BNP with the AxSYM assay using frozen plasma samples may not be valid under the conditions tested. In contrast, NT-proBNP as measured by the Elecsys assay may be stored at -20 degrees C for at least four months without a relevant loss of the immunoreactive analyte.     

Erythrocyte nucleotide stability and plasma hypoxanthine concentrations: improved ATP stability with short-term storage at room temperature

We have measured erythrocyte nucleotide concentrations at timed intervals over 24 h in heparinised blood stored at 4 degrees C, room temperature, or 37 degrees C. The objective was to determine whether the grossly altered NAD concentrations found in the erythrocytes of patients with two different inherited purine disorders could be related to altered stability or turnover rates. An unexpected finding was the improved stability of all erythrocyte nucleotides in blood stored at room temperature compared with 4 degrees C. Not only was the breakdown of ATP greater at 4 degrees C compared with room temperature, higher hypoxanthine concentrations were present in the plasma associated with a fictitious increment in inosine. NAD and NADP, by contrast, showed remarkable stability in both control and patient erythrocytes, irrespective of their original value. Although these studies failed to establish an explanation for the altered NAD levels in the patients, the superior ATP stability in blood stored at room temperature in the erythrocytes from both patients and controls suggests that current practices of storing blood on ice for short-term studies require re-evaluation.     

Effect of storage conditions on the CD34+ counts in flow cytometric analysis after anticoagulation of samples with EDTA

The transplantation of peripheral blood precursor cells (PBPC) is becoming of interest for autografting patients with a wide variety of haematological and other malignancies. For rapid quality control of PBPC apheresis products, flow cytometry is applied to quantify the number of CD34+ events. We studied the effect of different storage conditions on the number of CD34+ counts in EDTA-anticoagulated aliquots of PBPC grafts. Within 24 h, CD34+ signals decreased when samples were stored at room temperature (RT, 20 +/- 2 degrees C) compared to the results obtained directly after cytapheresis. The signal rate equalled or exceeded the baseline values after 24 h when aliquots were deposited at room temperature and subjected to agitation. Storage at 4 degrees C revealed no significant changes. These data indicate that quality control of PBPC samples by flow cytometry significantly depends on storages time, temperature and other conditions like the agitation of the specimen.     

Hydroxylamine technique for in vitro prevention of penicillin inactivation of tobramycin.

Hydroxylamine was evaluated and found to be a highly effective agent for the in vitro prevention of penicillin inactivation of tobramycin. This inactivation reaction resulted in an underestimation of tobramycin concentrations and was dependent on time, temperature, amount and type of penicillin, and amount of tobramycin. Plasma samples containing tobramycin and three clinically relevant concentrations of ticarcillin, carbenicillin, azlocillin, or piperacillin were incubated with and without hydroxylamine, and tobramycin concentrations were monitored at 0, 12, 24, 48, and 72 h. The inactivation reaction was found to be completely inhibited by hydroxylamine (1 mg/ml) compared with a 27 to 50% loss of measured tobramycin concentration in the unprotected tobramycin-penicillin samples. Hydroxylamine did not interfere with the Emit enzyme immunoassay (Syva Co.) at either high or low tobramycin concentrations. Hydroxylamine was effective in inhibiting the tobramycin inactivation at both room and refrigerator temperatures and was 100% effective in protecting tobramycin on a 1:1 molar basis.     

Stability of YKL-40 concentration in blood samples

The stability of YKL-40, a mammalian member of the family of 18 glycosyl-hydrolases, in blood samples handled under different temperatures and different time intervals before centrifugation was studied in paired serum and plasma samples from 25 healthy premenopausal Danish women. Significant elevations of YKL-40 were found in 8 paired serum samples left on the clot for more than 3 h at room temperature compared to paired serum samples left on the clot for 3 h or less. Significant elevations of YKL-40 were found in 8 paired plasma (EDTA) samples left on the blood cells for more than 8 h at room temperature compared to paired plasma (EDTA) samples left on the blood cells for 8 h or less. No elevations were found in YKL-40 levels in serum samples left on the clot at 4°C for 24 h or in plasma (EDTA) samples left on the blood cells for 72 h before centrifugation. Significantly lower concentrations of YKL-40 were measured in plasma (EDTA) compared with paired serum samples with a serum/plasma ratio of 1.4 in samples left on the clot or on blood cells at 4°C for up to 24 h. Repetitive freezing and thawing had no significant effect on the measured YKL-40 concentrations. In conclusion, we have shown that YKL-40 is very dependent on the handling procedures. All the blood samples must be processed into plasma (EDTA) within 8 h at room temperature or into serum in less than 3 h at room temperature. If this is not possible, the blood samples must be stored at 4°C until processed.     

Stability of YKL-40 concentration in blood samples

The stability of YKL-40, a mammalian member of the family of 18 glycosylhydrolases, in blood samples handled under different temperatures and different time intervals before centrifugation was studied in paired serum and plasma samples from 25 healthy premenopausal Danish women. Significant elevations of YKL-40 were found in 8 paired serum samples left on the clot for more than 3 h at room temperature compared to paired serum samples left on the clot for 3 h or less. Significant elevations of YKL-40 were found in 8 paired plasma (EDTA) samples left on the blood cells for more than 8 h at room temperature compared to paired plasma (EDTA) samples left on the blood cells for 8 h or less. No elevations were found in YKL-40 levels in serum samples left on the clot at 4 degrees C for 24 h or in plasma (EDTA) samples left on the blood cells for 72 h before centrifugation. Significantly lower concentrations of YKL-40 were measured in plasma (EDTA) compared with paired serum samples with a serum/plasma ratio of 1.4 in samples left on the clot or on blood cells at 4 degrees C for up to 24 h. Repetitive freezing and thawing had no significant effect on the measured YKL-40 concentrations. In conclusion, we have shown that YKL-40 is very dependent on the handling procedures. All the blood samples must be processed into plasma (EDTA) within 8 h at room temperature or into serum in less than 3 h at room temperature. If this is not possible, the blood samples must be stored at 4 degrees C until processed.     

The effect of different methods of storage on the results of serum total CO2 assays

Metabolic acidosis frequently complicates end-stage renal failure. In haemodialysis patients its severity is usually monitored by measurement of the total CO(2) (TCO(2)) level. Samples from 'satellite dialysis' patients are often stored prior to analysis. We investigated the affect of storage of 21 samples for 24 h under different conditions prior to analysis. If samples were stored at room temperature the TCO(2) fell from 22.7+/-4.2 mmol/l to 21.6+/-3.7 mmol/l (P=0.001). If the same samples were spun and stored at 4 degrees C the TCO(2) was 22.4+/-3.9 mmol/l (P=not significant). We conclude that the magnitude in the fall of TCO(2) stored at room temperature for 24 h is unlikely to be clinically significant and can be prevented by spinning the sample and refrigerating it.