Stability of urinary fractionated metanephrines and catecholamines during collection, shipment, and storage of samples

BACKGROUND: Measurements of 24-h fractionated urinary metanephrines and catecholamines are used for the diagnosis of pheochromocytoma, but adequate information is needed regarding collection, storage, and shipment conditions. METHODS: Spot urine samples were collected from 8 healthy volunteers. Aliquots were immediately frozen at -20 degrees C, or acidified to pH 4 and then frozen either directly or after 24 h at room temperature. The remaining urine was left at room temperature for 24 h and then split into one portion that was acidified and one portion that was not. Aliquots were either frozen or allowed to stand at room temperature for an additional 24, 48, 72, 96, and 168 h before freezing. We also tested the efficacy of adding Na(2)EDTA and Na(2)S(2)O(5), as an alternative to acidification for preservation of the catecholamines. RESULTS: No clinically relevant degradation (<5%) was observed for the fractionated metanephrines under any of the storage conditions. In contrast, in approximately 50% of the untreated samples catecholamines were partially degraded during the first 24 h at room temperature. Immediate acidification, however, prevented degradation, whereas acidification after 24 h prevented further decay. Addition of Na(2)EDTA and Na(2)S(2)O(5) fully prevented degradation of catecholamines during the first 24 h in 4 of 5 cases. In the remaining case, degradation did not exceed 10%. CONCLUSION: Preservation of samples for measurements of urinary fractionated metanephrines is not necessary if samples are assayed or frozen within 1 week, which is an important advantage if transport of samples is necessary. In contrast, urinary catecholamines require preservation measures during collection.     

24小时尿肌酐检测样本保存方法的探讨

目的分析尿液不同保存方法对24 h尿肌酐（UCr）检测值的影响,探讨留取24 h尿测定UCr的适宜保存条件。方法在同一时间收集尿液后,分别在不同保存时间、不同保存温度和加入不同防腐剂的条件下,检测初始和保存后的UCr浓度。采用单因素方差分析探讨时间、温度和防腐剂3种因素对UCr测定值的影响。结果在室温和4℃保存条件下,UCr均可稳定保持24 h,在24 h内测定值没有明显变化;加入甲醛会降低UCr测定值（P〈0.05）,而二甲苯对UCr测定值没有影响。结论留取24 h尿测定肌酐,只需将24 h尿在室温下放置即可,无需额外添加防腐剂。     

24h尿肌酐检测影响因素的探讨

目的 分析尿液不同保存方法和检测方法对24 h尿肌酐(Ucr)的影响,探讨留取24 h尿测定肌酐的适宜保存条件和最佳检测方法.方法 在同一时间收集24 h尿液后,分别在不同时间加入不同防腐剂及采用不同检测方法的条件下,检测初始和保存后的肌酐浓度,采用单因素方差分析探讨时间、防腐剂和检测方法3种因素对Ucr测定值的影响.结果 在室温条件下,Ucr在24 h内均可保持稳定,没有明显变化;加入甲醛会降低Ucr检测值(P<0.05),加入12 mmol/L浓盐酸并调节pH至4.08,也会降低Ucr检测值(P<0.05),而二甲苯对Ucr检测值没有影响(P>0.05);采用肌酐酶法检测的Ucr值低于苦味酸法(P<0.01).结论 测定24 h Ucr只需在室温下放置24 h后,直接采用肌酐酶法进行检测,无需添加任何防腐剂.     

Preanalytical variables and off-site blood collection: influences on the results of the prothrombin time/international normalized ratio test and implications for monitoring of oral anticoagulant therapy

BACKGROUND: The quality of oral anticoagulant therapy management with coumarin derivatives requires reliable results for the prothrombin time/International Normalized Ratio (PT/INR). We assessed the effect on PT/INR of preanalytical variables, including ones related to off-site blood collection and transportation to a laboratory. METHODS: Four laboratories with different combinations of blood collection systems, thromboplastin reagents, and coagulation meters participated. The simulated preanalytical variables included time between blood collection and PT/INR determinations on samples stored at room temperature, at 4-6 degrees C, and at 37 degrees C; mechanical agitation at room temperature, at 4-6 degrees C, and at 37 degrees C; time between centrifugation and PT/INR determination; and times and temperatures of centrifugation. For variables that affected results, the effect of the variable was classified as moderate when <25% of samples showed a change >10% or as large if >25% of samples showed such a change. RESULTS: During the first 6 h after blood collection, INR changed by >10% in <25% of samples (moderate effect) when blood samples were stored at room temperature, 4-6 degrees C, or 37 degrees C with or without mechanical agitation and independent of the time of centrifugation after blood collection. With one combination of materials and preanalytical conditions, a 24-h delay at room temperature or 4-6 degrees C had a large effect, i.e., changes >10% in >25% of samples. In all laboratories, a 24-h delay at 37 degrees C or with mechanical agitation had a large effect. We observed no clinically or statistically relevant INR differences among studied centrifugation conditions (centrifugation temperature, 20 degrees C or no temperature control; centrifugation time, 5 or 10 min). CONCLUSIONS: We recommend a maximum of 6 h between blood collection and PT/INR determination. The impact of a 24-h delay should be investigated for each combination of materials and conditions.     

干化学法和湿化学法对24h 尿蛋白定量检测的比较及样本保存条件研究

目的 比较罗氏Cobas 501和天津果实Hipee M1生化分析仪24h尿蛋白定量检测结果的一致性,探讨样本保存条件对检测结果的影响。方法 使用Cobas 501和Hipee M1两台生化分析仪分别对119例尿液常规标本进行24h尿蛋白定量检测,比较检测结果的相关性和一致性。通过混合尿液样本进行不同保存环境以及添加不同防腐剂测试,研究24h尿蛋白样本保存方法对测试结果的影响。结果 两台生化分析仪的质控检测结果的变异系数分别为2.31%～5.61%和3.25%～5.22%,具有很好的重复性。两台生化分析仪尿液样本检测结果经回归分析,检测结果的一致性符合要求,差异无统计学意义(r=0.991,P>0.05)。尿液样本(2～8)℃冷藏保存、使用防腐剂二甲苯和硼酸在常温条件下保存,24h尿蛋白在各个时间点的检测结果,差异均无统计学意义(P>0.05)。结论 Cobas 501和Hipee M1两台仪器之间无明显差异,均具有较高的稳定性,使用硼酸作为防腐剂可用于尿液样本的常温保存。     

Different stability of free and complexed prostate-specific antigen in serum in relation to specimen handling and storage conditions.

The effect of sample collection, storage conditions (time and temperature), and freeze-thaw cycles on the stability of free prostate-specific antigen (fPSA), PSA complexed with alpha1-antichymotrypsin (ACT-PSA), and total PSA (tPSA) in serum was studied. The analytes were quantified using immunoassays for tPSA and fPSA on the Elecsys system 2010 and a research assay for ACT-PSA on the ES system (Roche Diagnostics). The stability of the analytes was calculated as percentages of the values measured in samples 1 h after blood collection. When the samples were stored at 37 degrees C, at room temperature or at 4 degrees C, the stability of ACT-PSA was less impaired than that of fPSA. To avoid erroneous results in the determination of PSA isoforms and their corresponding ratios, serum samples should be preserved at 4 degrees C when the analysis is performed within 8 h after blood collection, or they should be stored at -80 degrees C if the analysis is not feasible during that period.     

标本类型和储存条件对促肾上腺皮质激素检测结果稳定性的影响

目的探讨标本类型和储存条件对促肾上腺皮质激素(ACTH)检测结果稳定性的影响。方法将标本分成血浆组和血清组,每组各57例,并在抽血后1h内检测ACTH浓度。在血浆组中选取30例血浆量充足的标本分成室温组、冷藏组和冷冻组,每组各30例,其中室温组和冷藏组在2、24、121h时检测ACTH浓度,冷冻组在24、121h时检测ACTH浓度。检测结果与设定的标准值进行比较分析。结果血清组ACTH水平明显低于血浆组,差异有统计学意义(P0.05)。室温组在2、24、121h时的检测结果与标准值比较差异有统计学意义(P0.05);冷藏组在2、24h时的检测结果与标准值比较差异无统计学意义(P0.05),而在121h时的检测结果与标准值比较差异有统计学意义(P0.05);冷冻组在24、121h时的检测结果与标准值比较差异无统计学意义(P0.05)。结论采用乙二胺四乙酸二钾抗凝标本检测ACTH时,在低温下应于1h内完成检测;若24h内不能完成检测时,应将分离的血浆冷冻储存于-20℃,其在121h内检测结果变化相对稳定。     

Evaluation of a new radioimmunoassay for urinary albumin

We have evaluated a new commercially available radioimmunoassay kit for albumin determination in urine. The assay is precise; within-run precision (CV) in the clinically significant ranges is 1.8-3.5%, between-run, 1.2-8.5%. The minimum detection limit was 0.6 micrograms/ml. Analytic recovery of different concentrations of albumin added to urine ranged from 98% to 103%. Samples, stored in plastic containers, were stable at room temperature for periods up to 7 days. Mean albumin excretion rates, measured in 20 normal volunteers for 3-h and 24-h periods during the same day were similar (7.1 +/- 4.6 [SD] versus 6.5 +/- 5.0 micrograms/min). In 8 normal subjects, 3-h excretion rates measured daily for 5 days showed no significant variability. In eight insulin-dependent diabetic subjects, albumin excretion measured in short periods of urine collection (3 h) were also in close agreement with 24-h collections (24.7 +/- 28.9 versus 17.6 +/- 18 micrograms/min). From these results it appears that this commercially available kit is suitable for conveniently monitoring microalbuminuria in large numbers of patients in research studies as well as for office practice. Such widespread use should make it possible to better determine the clinical usefulness of this test in the management of diabetic patients.     

The clinical significance of dilatation of the collecting system in the transplanted kidney

The significance of dilatation of the collecting system of the transplanted kidney and its relationship to bladder distention was reviewed in 39 renal recipients examined by sonography (94 studies). The degree of pelvicaliceal (PCS), ureteral, and bladder distention was graded and correlated with the 24-h urine output, nuclear renal scan, and clinical follow-up. marked PCS distention can indicate obstruction (33%), especially when there is no associated bladder distention (60%) and a fluid collection lies along the path of the ureter. The 24-hr urine output did not influence the degree of PCS distention.     

Protein:creatinine ratio in random urine samples is a reliable marker of increased 24-hour protein excretion in hospitalized women with hypertensive disorders of pregnancy

BACKGROUND: The protein:creatinine ratio in random, untimed urine samples correlates with 24-h protein excretion in pregnant women with and without hypertension. Nevertheless, whether this ratio is appropriate as a screening test for proteinuria is still unclear, in part because of the paucity of large studies. METHODS: We measured protein:creatinine ratios in random urine samples and protein contents of 24-h urine samples in a cross-sectional study of 927 hospitalized pregnant women at >/=20-weeks of gestational age and in a 2nd cohort of 161 pregnant women. In the 2nd group, urine specimens were obtained before and after completion of the 24-h collections, avoiding 1st-morning void specimens. RESULTS: Protein excretion was >/=300 mg/24 h in 282 patients (30.4%). The urine protein:creatinine ratio and the 24-h protein excretion were significantly correlated (r = 0.98, P <0.001). The protein:creatinine ratio as an indicator of protein excretion >/=300 mg/24 h was >/=0.3. The sensitivity and specificity were 98.2% and 98.8%, respectively. Positive and negative predictive values were 97.2% and 99.2%, respectively, and positive and negative likelihood ratios were 79.2 and 0.02, respectively. The diagnostic accuracy of the urinary protein:creatinine ratio was corroborated in the 2nd cohort of patients, which also showed no statistically significant difference in protein:creatinine ratio between samples obtained >24 h apart. CONCLUSIONS: Random urinary protein:creatinine ratio is a reliable indicator of significant proteinuria (>300 mg/day) in nonambulatory pregnant women, irrespective of sampling time during the daytime. The protein:creatinine ratio may be reasonably used as an alternative to the 24-h urine collection method.     

Ultrastructure of human platelets processed for transfusion under standard blood bank conditions

Platelets processed for transfusion are routinely subjected to centrifugation, mechanical agitation and storage at either room temperature or 4 C. To evaluate morphologic changes associated with standard blood bank conditions, platelet units were grouped into four categories: linear agitation at room temperature, agitation at a 90 degrees arc with a Hemolater at room temperature, agitation at a 360 degrees arc with a commercial platelet agitator, and refirgeration at 4 C without agitation. Cold (4 C) preservation resulted in a surprisingly good preservation of platelet ultrastructure, even at 72 hours of storage. By contrast, harsh linear agitation at room temperature brought about marked alterations in platelet ultrastructure beginning at 24 hours. The Hemolator agitator with 90 degrees arc was associated with good preservation of platelet organelles even at 72 hours, whereas marked degenerative changes were observed at this time in platelets processed with a commercial agitator with a 360 degrees arc. These results indicate that platelets stored at 4 C or processed at room temperature with an agitator with 90 degrees arc show the best preservation of ultrastructure.     

尿儿茶酚胺标本留取方法的改进性研究

目的对尿儿茶酚胺标本留取方法进行改进,探索避免尿儿茶酚胺衰减的更好的标本留取方法。方法选取10例健康人随机留取尿标本,留尿完毕立即测定儿茶酚胺的含量做为原始值,再将每人标本分成3管每管10 ml,分别加入不同浓度的盐酸,室温24 h后测定其儿茶酚胺含量,并与原始值做比较。结果 6 mol/L盐酸含量为0.5%以上的尿标本经过24 h室温保存后儿茶酚胺衰减最小,与原始值做比较无差异(P>0.05)。结论根据患者尿量调整盐酸用量的标本防腐效果要好于使用固定盐酸用量的方法。     

Stability of prothrombin time and activated partial thromboplastin time tests under different storage conditions

Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are common laboratory tests that are useful in the diagnosis of coagulation disorders and monitoring anticoagulant therapy. Recent expansions in the outreach laboratory services at our institution prompted us to investigate the shipping limitations for some tests, including PT and aPTT. Although we followed NCCLS guidelines for the collection of blood specimens, we observed falsely elevated PT and aPTT values due to the different storage conditions. The objective of this study is to determine the effect of conditions and duration of storage on PT and aPTT tests using plasma and whole blood samples, respectively. For this study, 36 plasma samples with normal and prolonged PT and aPTT were exposed to different storage conditions. Blood was centrifuged immediately and plasma was stored at room temperature (RT), refrigerated at 4°C, or frozen at −20°C. The samples were analyzed at 0 h and repeated at 6, 12 and 24 h under various conditions. Although statistically significant differences were observed for plasma samples for normal PT tests after 12 h at refrigerated and frozen storage conditions, the differences would not change the clinical interpretation of the results. On the other hand, samples stored refrigerated or at RT showed significant differences for aPTT at 24 h. These differences would change clinical interpretation, especially for samples with normal or near normal aPTT times. Interestingly, aPTT was significantly higher for samples stored frozen when compared to refrigerated and RT conditions at 6 h. Similar patterns were also observed on ten whole blood samples with normal PT and aPTT values. In conclusion, either plasma or whole blood samples can be accepted for PT testing up to 24 h and for aPTT testing up to 12 h only, when transported either at RT or at 4°C.     

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.     

防腐剂对24 h尿蛋白定量检测的影响

目的：分析防腐剂对24 h尿蛋白检测结果的影响,探讨留取24 h尿测定尿蛋白加入防腐剂的必要性。方法在同一时间收集健康体检者尿蛋白定性为阴性的尿液后,加入不同量蛋白标准品和大肠杆菌菌液,检测初始和室温保存24 h 后的尿蛋白水平。采用单因素方差分析探讨3种蛋白浓度梯度下,含不同细菌数的尿液室温保存24 h后清蛋白水平变化。结果在保存于室温,不加防腐剂的情况下,不同蛋白浓度且含不同细菌数的尿液蛋白浓度测定值可稳定保持24 h,在24 h内测定值没有明显改变（P＞0．05）。结论用于24 h尿蛋白定量检测的标本可以不加入防腐剂。     

Influence of time and storage conditions on plasma HIV viral load measurements

Quantification of human immunodeficiency virus (HIV) RNA in plasma from HIV-infected patients is now widely used as a clinical indicator of disease prognosis and of response to antiretroviral therapy. However, controversy exists as to whether values obtained under different testing conditions could vary significantly, thus jeopardizing the appropriate interpretation of data. Herein, we demonstrate that results obtained after testing plasma versus whole blood, or immediate versus deferred processing, do not appear to influence viral load measurements significantly. Thirty blood samples from HIV-infected patients were analysed. The second generation branched-DNA assay was used for quantification of plasma viral load. HIV RNA remained stable for at least 24 h at room temperature, either in plasma or in whole blood, in 72.4% of the samples (< 0.2 log difference in viral load values) although lower levels of HIV RNA tend to be seen in samples after being stored as whole blood at room temperature. Only 3.4% of samples showed a decline > 0.5 log when they were left as whole blood at room temperature for 24 h in comparison with testing after immediate plasma separation. Although immediate separation and refrigeration of plasma samples may reduce the chance of significant falls in viral load measurements, this level of processing can be limited in regions where clinical blood samples cannot be processed rapidly. Our data provide confidence in the results obtained when testing specimens, either plasma or whole blood, 24 h after venepuncture and storage at room temperature, mimicking the conditions in the transport of blood samples to reference centres.     

Single-void urine samples can be used to estimate quantitative microalbuminuria

The excretion of small quantities of urinary albumin (microalbuminuria) may predict renal failure in diabetes. The measurement of microalbuminuria with radioimmunoassays has been based on 24-h, overnight, and 3- to 4-h collections. To determine whether single-void urine samples can be used to estimate 24-h excretion, we compared the results of 24-h outpatient urine collections with single-void samples corrected for creatinine from diabetic and nondiabetic subjects. The overall correlation of single-void sample results expressed as microgram albumin per milligram creatinine with 24-h excretion (mg/24 h) was excellent (r = .82, P less than .001). More important, in the diabetic patients the sensitivity and specificity of detecting 24-h microalbuminuria in the abnormal range were at least 94 and 96%, respectively. Single-void urine specimens adjusted for creatinine discriminate between normal and abnormal levels of microalbuminuria, as determined in 24-h urine collection, with high specificity and sensitivity.     

Stability of the long chain non-esterified fatty acid pattern in plasma and blood during different storage conditions

A study has been carried out to determine the conditions under which plasma and blood can be stored without significant changes in the non-esterified fatty acid (NEFA) pattern and in the total NEFA concentration. From the results obtained it appears that: (1) blood can be stored for 2 h at room temperature and for 48 h at 4 degrees C. (2) plasma can be stored for 6 h at room temperature, 48 h at 4 degrees C and for at least 10 days at -20 degrees C under nitrogen without significant changes in the NEFA pattern and in the total NEFA concentration. The possible influence of heparin, used as anticoagulant, has been investigated. The results obtained are compared with those of other investigators.     

The alterations of the activities of coagulation inhibitors and fibrinolytic factors in stored cord blood could affect the yield of progenitor cells during processing

We assessed the changes in the activities of hemostatic variables by the storage temperature and time interval between collection and separation of cord blood (CB) and analyzed their relationship with the yield of progenitor cells during processing. Total nucleated cell (TNC) and CD34+ cell counts were significantly higher in the CB stored at ambient temperature than at 4 degrees C. The significant loss of TNC and CD34+ cells continued to 24 h after collection in CB stored at 4 degrees C, but loss of TNC began only after 24 h at ambient temperature. There were no changes in the plasma activities of antithrombin III (ATIII) and plasminogen. The activity of protein C was decreased significantly until 24 h after collection, particularly in CB stored at 4 degrees C. The activity of alpha2-antiplasmin was decreased until 24 h in CB stored at 4 degrees C and from 24 h in CB stored at ambient temperature. These data suggest that the alterations in the activities of coagulation inhibitors and fibrinolytic factors could be an important factor in coagulability, particularly in CB stored at 4 degrees C compared to ambient temperature, and also affect the yield of progenitor cells in processed CB.