R B McComb’s research while affiliated with Hartford Hospital and other places

What is this page?


This page lists works of an author who doesn't have a ResearchGate profile or hasn't added the works to their profile yet. It is automatically generated from public (personal) data to further our legitimate goal of comprehensive and accurate scientific recordkeeping. If you are this author and want this page removed, please let us know.

Publications (76)


State-wide hospital clinical laboratory plan for measuring cholinesterase activity for individuals suspected of exposure to nerve agent chemical weapons
  • Article

February 2008

·

21 Reads

·

5 Citations

·

·

Robert McComb

·

[...]

·

Katherine Kelly

Hospital laboratories currently lack the capacity to provide emergency determination of cholinesterase activity. We have developed a hospital-based 3-tiered system to test plasma for butyrylcholinesterase (BChE) activity and whole blood for red cell acetylcholinesterase (AChE) activity using available technology and personnel. Interagency communications, toxidrome definition, and patient triage will be coordinated by the Connecticut Department of Public Health and the Poison Control Center. Initial BChE data documents good precision between institutions (coefficient of variation < 8%). Laboratory testing of plasma or blood for cholinesterase activity is important in the management of nerve agent exposure and in ruling out disease in those with non-specific symptoms in the setting of a terrorist attack or accidental exposure. Rapid availability of strong hospital-based analytic support in a smoothly functioning network of clinical, public health, and laboratory services will facilitate overall regional response to chemical terrorism or large scale HazMat events.


Investigation of N-Methyl-D-Glucamine Buffer for Assay of Alkaline Phosphatase in Serum

December 1992

·

18 Reads

·

6 Citations

Clinical Chemistry

We evaluated N-methyl-D-glucamine (MEG) as a buffer for assay of alkaline phosphatase (ALP; EC 3.1.3.1) and compared the MEG-based assay with the current International Federation of Clinical Chemistry Reference Method for ALP (IFCC/RM/ALP), in which 2-amino-2-methyl-1-propanol (AMP) is the pH buffer. The ALP assay in MEG at 30 and 37 degrees C shows excellent correlation with the IFCC/RM/ALP at 30 degrees C, but yields proportionately higher ALP activities (8.2% at 30 degrees C and 57% at 37 degrees C). ALP is unstable in both MEG and AMP at 37 degrees C. Serum incubated in MEG undergoes a pH-dependent biphasic loss of ALP activity: an initial rapid 5% loss after 1 min of incubation and a 10% loss per hour thereafter. A similar pattern was seen for incubation with AMP. The use of a serum-initiated reaction (no preincubation of enzyme with buffer) eliminated the early loss in activity. The addition of the metal ion buffer N-hydroxyethylethylenediaminetriacetic acid, along with low concentrations of Zn and Mg, as used in the IFCC/RM/ALP, reduced the slow loss in activity over time, as did decreasing the reaction temperature to 30 degrees C, but had no effect on the early rapid decay in activity seen in the first minute. Moderate transphosphorylation (45%) and nonenzymatic hydrolysis (3.3 U/L) were observed with MEG under the conditions of the assay (37 degrees C). A comparison of different lots of MEG from two manufacturers showed no significant difference in ALP activities.


Proposed reference method for iron in serum used to evaluate two automated iron methods

November 1990

·

15 Reads

·

17 Citations

Clinical Chemistry

The manual Reference Method of the Centers for Disease Control for serum iron (CDC/RM/Fe) and a semiautomated adaptation of it were used to evaluate two working methods: one, a detergent solubilization procedure for the Roche Cobas-Bio analyzer, the other, the Kodak Ektachem 700 procedure, based on dry-film technology. The CDC/RM/Fe and its semiautomated version gave essentially the same results for 40 sera from hospital patients. This semiautomated version was in turn compared with the two working procedures in a study involving 200 patients. Each of the working methods correlated well with the semiautomated CDC/RM/Fe method. Separate recovery and interference studies indicated satisfactory analytical recovery of iron in all cases, but the detergent solubilization method was found to be susceptible to interference by hemoglobin, lipemia, and bilirubin.


Molar absorptivities of bilirubin (NIST SRM 916a) and its neutral and alkaline azopigments
  • Article
  • Full-text available

October 1990

·

584 Reads

·

17 Citations

Clinical Chemistry

Three laboratories in the U.S. and two in the Netherlands determined molar absorptivities (epsilon) of Standard Reference Material (SRM) 916a Bilirubin from the National Institute of Standards and Technology. In caffeine reagent the average epsilon values were 50,060 and 48, 980 L.mol-1.cm-1 at 432 and 457 nm, respectively. The epsilon value of the blue azopigment, obtained with the Reference Method for total serum bilirubin, was 76,490 L.mol-1.cm-1 at 598 nm. When the addition of alkaline tartrate was omitted, the molar absorptivity of the red azopigment was 56,600 L.mol-1.cm-1 at 530 nm.

Download

Evaluation of three first-generation ion-selective electrode analyzers for lithium: Systematic errors, frequency of random interferences, and recommendations based on comparison with flame atomic emission spectrometry

February 1990

·

22 Reads

·

26 Citations

Clinical Chemistry

Ion-selective electrode analyzers for measuring lithium (Li/ISE) in serum became available in early 1987. We compared results for patients' samples from three of them vs results from flame atomic emission spectrometry (FAES). Within-run and day-to-day imprecision ranged from 0.01 to 0.03 mmol/L and 0.01 to 0.04 mmol/L, respectively. Comparing Li/ISE results (y) with the FAES results (x) gave the following equations: y = 1.063x - 0.035 for AMDEV's Lytening 2, y = 1.020x + 0.038 for NOVA's Model 11, and y = 1.030x - 0.027 for AVL's Model 985. Unexplained positive errors greater than 0.2 mmol/L were observed for two of the 90 patients' samples, but only a few additional excessively high values were seen in 3000 patients' samples run subsequently (Lytening 2). Causes of error in clinical Li/ISE measurements are still unclear; simply characterizing them as "matrix effects" does not correct the underlying analytical problem. An increase in pH from loss of CO2 gave low results on two of the three Li/ISE analyzers but did not change FAES results. Trimethylammonium bicarbonate used in a reconstitution solution caused extremely high Li/ISE results but did not change FAES results. Performance specifications to help reduce and correct these errors are recommended.


Evaluation of a kinetic method for prostatic acid phosphatase with use of self-indicating substrate, 2,6-dichloro-4-nitrophenyl phosphate

July 1989

·

11 Reads

·

9 Citations

Clinical Chemistry

The purity, spectral characteristics, and rate of nonenzymatic hydrolysis of 2,6-dichloro-4-nitrophenyl phosphate (DCNPP) were determined. Rates of DCNPP hydrolysis by prostatic acid phosphatase (PAP) and erythrocytic acid phosphatase (EAP) (both EC 3.1.3.2) were measured in the absence and in the presence of various alcohols. 1.5-Pentanediol was the most effective transphosphorylation agent for specifically enhancing the activity of PAP. 1,4-Butanediol also enhanced PAP activity but markedly inhibited EAP activity. Bovine and human serum albumin preparations also accelerated the hydrolysis of DCNPP. DCNPP can be used for the continuous or multipoint-rate assay of PAP.


Emetine identified in urine by HPLC, with fluorescence and ultraviolet/diode array detection, in a patient with cardiomyopathy

April 1989

·

10 Reads

·

6 Citations

Clinical Chemistry

A 15-year-old girl with a four-month history of cardiac failure from undetermined cause was admitted to the hospital with weakness, fatigue, and weight loss. During her hospitalization she was found to have abused diet aids, laxatives, and cathartics. Although an electrocardiogram revealed nonspecific T-wave abnormalities and laboratory studies showed supranormal enzyme test results for creatine kinase and lactate dehydrogenase, no definite explanation of the cardiomyopathy was forthcoming. Ipecac abuse leading to cardiomyopathy was suspected early in the hospitalization. HPLC analysis of a urine sample showed emetine, a principle component of ipecac, the presence of which was later confirmed by more-specific HPLC analysis with photodiode array detection.


Table 1 . 
Evaluation of the IFCC reference method for alanine aminotransferase: Spurious blank ALT activity due to contamination of D-alanine with L-alanine, and recommendations for a correction

February 1989

·

141 Reads

·

7 Citations

Clinical Chemistry

During an evaluation of the IFCC reference method for alanine aminotransferase (ALT, EC 2.6.1.2), we noted that the specimen blank activity reaction was markedly increased. Experience with five different lots of D-alanine from four commercial sources indicated that substantial and varying negative bias (up to -10%) could be introduced into the blank-corrected ALT activity, depending on the lot of D-alanine used. Although the IFCC procedure for ALT mentions the possibility of this L-alanine contamination, we believe that the degree of contamination in commercial reagents is underestimated. Analyzing the five lots of D-alanine for L-alanine, we found the magnitude of negative bias to be correlated directly with L-alanine contamination. Here, we describe a quick, sensitive assay based on coupled reactions of L-amino acid oxidase/peroxidase for quantifying L-alanine in the concentration range of 0-15 mmol/L without a sample-dilution step. Results by this alternative L-alanine assay agreed well with those recommended in the IFCC ALT procedure. Further examination suggested an even simpler solution to the L-alanine contamination problem, because we found no difference in the blank-corrected ALT activity determined in Tris HCl buffer, with or without D-alanine (free of L-alanine). We therefore propose that D-alanine be omitted from the IFCC reference ALT procedure.


Lidocaine metabolite and creatinine measurements in the Ektachem 700: Steps to minimize its impact on patient care

November 1988

·

15 Reads

·

20 Citations

Clinical Chemistry

The single-slide method used for creatinine in the Kodak "Ektachem" analyzer is far more precise than the two-slide method. We confirm that sera from patients on intravenous therapy with lidocaine exhibit a positive bias in results for creatinine but that lidocaine itself does not interfere. Instead, N-ethylglycine, a metabolite of lidocaine with a structure similar to that of sarcosine, is probably the cause. A method that allows N-ethyglycine to be measured directly is described. We followed the degree of this interference through five generations of the slide. Our investigations include two detailed comparison studies between the Kodak Ektachem 700 and the Beckman Astra analyzers. Creatinine determinations on lidocaine-treated patients when first-generation slides were used averaged 4.6 mg/L higher than determinations on these same specimens performed in the Astra. Serum creatinine results from patients not on lidocaine showed no significant difference between the two instruments. The average difference in generation 2, 3, and 4 slides was 0.24, 0.22, and 2.5 mg/L, respectively. No more than 2% of our creatinine results had a clinically significant lidocaine-related bias. We show how to identify and correct this small proportion of results that are biased because of lidocaine therapy.



Citations (45)


... Lidocaine and its metabolites, monoethyglycinexylidide (MEGX) and glycinexylidide (GX), and K were analyzed using a modified extraction method of Flood et al. (1980). Briefly, previously frozen plasma samples were thawed and vortexed and 1 mL was transferred to a clean test tube containing 25 lL of internal standard (50 lg mL )1 trimethomprim). ...

Reference:

Effect of intravenous lidocaine and ketamine on the minimum alveolar concentration of isoflurane in goats
Simultaneous liquid-chromatographic determination of three antiarrhythmic drugs: disopyramide, lidocaine, and quinidine.
  • Citing Article
  • February 1980

Clinical Chemistry

... 5⋅10 − 4 M, 1.0⋅10 − 4 M, 5.0⋅10 − 4 M, 2.5⋅10 − 5 M, 1.0⋅10 − 4 M) and 4.5⋅10 − 4 M in NaBH 4 and measuring their absorbance using an in situ Agilent Cary 3500 UV-Vis Spectrometer equipped with 1 cm path cuvette. In agreement with the literature, the average extinction coefficient derived from the calibration curves repeated three times is 18,900 M − 1 cm − 1[19,20]. ...

High-purity 4-nitrophenol: purification, characterization, and specifications for use as a spectrophotometric reference material.
  • Citing Article
  • May 1980

Clinical Chemistry

... The serum AST was detected as previously reported (Tietz, 1986). The LDH assay was stated by (Wacker et al., 1956) and later qualified by (Gay et al., 1968). The determination of serum CK-MB described by (Tietz, 1986) and serum Troponin 1 was determined according to (Etievent et al., 1995). ...

Optimum Reaction Conditions for Human Lactate Dehydrogenase Isoenzymes as They Affect Total Lactate Dehydrogenase Activity
  • Citing Article
  • August 1968

Clinical Chemistry

... As a result, adult HPP is highly underdiagnosed. A few years ago, some laboratories only indicated the 'high' cut-off and, in the absence of personal knowledge of the lower normal cut-off, the ALP drop was not always noticed, 16 and therefore, easily overlooked. 17 In our study, many patients had not ...

Alkaline Phosphatase
  • Citing Book
  • January 1979

... In connective tissue, TN-AP is mainly expressed in bone and cartilage, but is also expressed in fibroblasts in periodontal ligament where physiological mineralization occurs [3,4,5]. Besides in connective tissue, TN-AP is also highly expressed in renal epithelial cells and capillary/arteriole endothelial cells [8][9][10]16], where pathological mineralizations such as nephrocalcinosis and vascular calcification sometimes occur. In this article, we focus on whether AP plays a role in the mineralization of tissues apart from bone and cartilage. ...

Distribution in Nature
  • Citing Chapter
  • January 1979

... ALPs hydrolyze a large variety of organic monophosphate esters with formation of an alcohol or phenol and a phosphate ion. Several methods have been described over the years based on the use of different substrates and different assay conditions (i.e., pH, buffers, reaction temperature) [76]. Currently, most tests used today on automated clinical chemistry analysers that measure the total ALP activity in serum use conventional photometric assay with the following reactions: ALP catalyzes the hydrolysis of p-nitrophenylphosphate (p-NPP), which is colorless, to phosphate and free p-nitrophenol (p-NP). ...

Measurement of Alkaline Phosphatase Activity
  • Citing Article
  • January 1979

... The most reliable parameter was the increase in the activity of the enzyme alkaline phosphatase. The CSF of patients without neurological disorders contains little or no activity as it was also shown in our control group (McComb et al., 1979). According to a previous human study, the CSF alkaline phosphatase activities of patients with meningitis and other neurological disorders varied in direct correlation with the number of polymorphonuclear leukocytes present and with the protein concentration (McComb et al., 1979). ...

Clinical Utilization of Alkaline Phosphatase Measurements
  • Citing Article
  • January 1979

... These are the sympathomimetics and other similar molecules that cause assay interference. 111,112 Importantly, this list includes paracetamol, which is metabolised to catechol compounds with a high incidence of chromatographic interference. 64 Whilst drugs have not been reported to cause false negative results, alpha-2 receptor agonists and dopamine agonists have been reported to lower catecholamine and metanephrine concentrations. ...

Pseudopheochromocytoma and Cardiac Arrest Associated With Phenylpropanolamine
  • Citing Article
  • March 1985

JAMA The Journal of the American Medical Association

... However, clinically, histopathological examination of tissue damage cannot be easily carried out on a living patient. Hence, there are set of cytosolic and some membrane-bound enzymes called tissue damage biomarker enzymes, which, when their activities are high in the blood of any patient, indicate tissue damage and leakages of cell membranes (Bowers and McComb 1975;Bode and Bode 2003;Young et al. 2006;Ding et al. 2012;Arulmozhi et al. 2012;Kim et al. 2017;Akinloye et al. 2021). Measurement of GGT activity was introduced in the 1970s as a marker hepatic dysfunction due to excessive alcohol consumption (Bulusu and Sharma 2016). ...

Measurement of Total Alkaline Phosphatase Activity in Human Serum
  • Citing Article
  • January 1976

Clinical Chemistry