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S Shahangian

Publications and source records attributed to S Shahangian.

At least 19 recordsLinked to original sources
PubMed2000

Variability of laboratory test results.

Variabilities of serum total cholesterol and potassium results provided to 11 medical clinics were assessed using an audit sample-split specimen design. This involved collection of 3 tubes of blood from each of 302 patients, with 1 split specimen divided into 3 audit samples: 1 was sent to the original participating laboratory, another to a commercial referral laboratory, and the third to an academic referee laboratory. Two methods were used to assess variability of test results. Method 1 was based on result pairs corresponding to the split specimen and its corresponding audit sample. Method 2 was based on audit sample results only. The 2 methods provided comparable results for total cholesterol; the estimated coefficient of variation was 1.0% to 3.7%. However, method 1 consistently provided higher estimates of variability for potassium; the estimated SD was 0.096 to 0.168 mmol/L for method 1, while it was 0.035 to 0.090 mmol/L for method 2. Method 1 is more practical, but method 2 can provide a more accurate assessment of analytic variability.

Cholesterol↗
PubMed2000

Toward optimal PT use.

Explore the source record for details and available documents.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1999

System to monitor a portion of the total testing process in medical clinics and laboratories: evaluation of a split-specimen design.

To evaluate a split-specimen design to identify problems in the testing process in hospital and physician office laboratories, we examined the testing for serum total cholesterol (n = 646) and potassium (n = 732) at 11 medical clinics evaluating 30-199 patients (mean, 125). Clinic personnel collected three tubes of blood from each patient. One specimen was processed routinely, the second was sent to a referral laboratory (RL), and the third specimen was sent to a holding facility for storage. The corresponding stored sample was retrieved and divided into three audit samples randomly and when result difference for the first two specimens exceeded critical values; one audit sample was sent to the original participant, the second to the RL, and the third to a referee laboratory. When three criteria were used, the result discrepancy rates were 2.5-8.7% for potassium and 1.5-4.6% for cholesterol. The split-specimen design could be implemented and evaluated as a monitoring system for a portion of the testing process.

Adolescent↗
PubMed1998

Proficiency testing in laboratory medicine: uses and limitations.

OBJECTIVE: To provide a critical review of recently published literature on the effectiveness, uses, and limitations of proficiency testing (PT) as a mechanism for laboratory improvement, and to explore ways to improve the PT process. DATA SOURCE: All publications identified by a MEDLINE search of the literature dating back to 1987 on the subject of "proficiency testing" in laboratory medicine, as well as selected references cited in recent review articles. STUDY SELECTION: No specific selection criteria were used for inclusion of publications identified by the MEDLINE database as long as they dealt with PT as a mechanism of medical laboratory improvement or a measure of laboratory performance. DATA EXTRACTION: Abstractions of data were made depending on relevance of the data. DATA SYNTHESIS: Proficiency testing data are an indicator, but not a measure, of laboratory performance. Limitations of current PT practices are incomplete assessment of the total testing process, PT materials being treated differently than those from patients, PT performance criteria, and "matrix effect." Proficiency testing performance has been related to length of PT experience, test environment and volume, institutional size, laboratory and analyst workload, difficulty of PT materials, performing quality control, testing methodology, and degree of automation. CONCLUSIONS: Proficiency testing has a well-established role as both a laboratory improvement and an educational tool. There are, however, several practical and design limitations even for the best-administered PT programs. Suggestions to improve the PT process include increased reliance on PT results in combination with other quality indicators (such as performance in regional surveys), occasional use of "blind" PT, introduction of biological materials to PT participants, electronic grading and reporting of PT results, and introduction of challenging PT materials to fulfill the educational role of PT.

Clinical Competence↗
PubMed1998

A system to monitor a portion of the total testing process in medical clinics and laboratories: feasibility of a split-specimen design.

OBJECTIVE: The purpose of this study was to assess the feasibility of using a prototype split-specimen design to assess integrity of a portion of the total testing process in medical clinics and laboratories. DESIGN: Two or three tubes of venous blood were collected from 177 patients for analysis of one of three analytes (serum potassium, serum total cholesterol, and whole-blood hemoglobin). Patients were seen at one of the nine clinics participating in this study. In all cases, one tube of blood from each patient was sent to a commercial referral laboratory, and the other tube(s) forwarded to the laboratory that routinely tested specimens for the clinic (participating laboratory) for analysis. Each participating laboratory removed a preanalysis and sometimes a post-analysis aliquot from each specimen and forwarded these to the referral laboratory for analysis. SETTING: The study was conducted in six physician office laboratories (three serving 1 to 4 [mean, 2.7] internists and three serving 3 to 24 [mean, 12] family physicians) and three hospital laboratories (serving hospitals with 100 to more than 700 beds). PATIENTS: Study patients were voluntary participants and provided informed consent. Patient age ranged from 18 to 80 years, and for all the laboratory test was specifically ordered for clinical reasons. Patients who were unable or unwilling to provide informed consent, those for whom testing would require that they provide more than 100 mL of blood, those whose blood was being collected by fingerstick, and those with results that were part of a laboratory test profile were excluded. MAIN OUTCOME MEASURES: Two main outcome measures were assessed: (1) percent differences between split-specimen results exceeding the maximum allowable imprecision level, which was based on published biological variation data (defined as one-half of the intraindividual percent coefficient of variation), for each analyte (result discrepancies); and (2) all "problems" (defined as departures from standard operating procedures) that could be documented by retrospective review of all relevant medical and laboratory records. RESULTS: The rate of result discrepancies was 1 in 20 (5%) for patients in whom hemoglobin was analyzed, 12 in 57 (21%) for patients in whom potassium was analyzed, and 1 in 60 (2%) for patients in whom total cholesterol was analyzed. Results of samples obtained during the aliquoting and storage phases of the total testing process were subject to study-induced problems and were generally not useful in tracing problems to specific stages of the testing process. A total of 28 problems (involving 26 patients) were documented, but only 6 problems were due to routine testing processes. CONCLUSIONS: The feasibility and limitations of a split-specimen design to detect result discrepancies were demonstrated. Most documented problems (22 of 28, or 79%) were study induced. To assess integrity of the total testing process, such problems need to be avoided.

Adolescent↗
PubMed1992

Concentration dependencies of immunoturbidimetric dose-response curves: immunoturbidimetric titer and reactivity, and relevance to design of turbidimetric immunoassays.

To characterize polyclonal antisera for two-point immunoturbidimetric applications, we defined, as functions of antiserum concentration, two parameters derived from dose-response curves: the maximum bichromatic optical response, Tmax, and the antigen concentration in the region of excess antibody corresponding to one-half Tmax, or C50. We raised monospecific polyclonal antisera in goats against several human immunoglobulins, C-reactive protein, C3, C4, apolipoproteins A-I and B, and several other proteins. We could linearly relate the logarithm of the antiserum concentration to log C50 and to log Tmax. The concentration of polyethylene glycol affected not only C50 and Tmax but also their functional dependencies on antiserum concentration. We devised two definitions of immunoturbidimetric titer and related them to the titer obtained by the single radial immunodiffusion method of Becker (Immunochemistry 1969; 6:539-46).

Apolipoprotein A-I↗
PubMed1991

Plasma protein-bound sialic acid in patients with colorectal polyps of known histology.

Protein-bound sialic acid (PBSA) was measured in serial plasma specimens from 62 healthy subjects, 48 patients with colorectal polyps, and 30 patients with colorectal adenocarcinomas. The mean plasma PBSA concentration in healthy smokers was significantly greater than that in healthy nonsmokers and healthy ex-smokers (P less than 0.0001). Villoglandular polyps were associated with higher plasma PBSA values than were the most benign hyperplastic polyps (P less than 0.025). Patients with the most neoplastic villoglandular and villous polyps had significantly greater (P less than 0.010-0.050) plasma PBSA values than healthy subjects. Polypectomy decreased the mean PBSA value significantly to the mean value for healthy subjects only for patients with villoglandular (P less than 0.010) or villous (P less than 0.050) polyps. Colorectal cancer patients had mean plasma PBSA concentrations significantly greater than those for the healthy subjects (P much less than 0.001) and the polyp patients (P much less than 0.001). Surgery significantly reduced (P less than 0.025) the mean PBSA value for the cancer patients to the mean PBSA value observed for the healthy subjects.

Adenocarcinoma↗
PubMed1991

Carcinoembryonic antigen in serum of patients with colorectal polyps: correlation with histology and smoking status.

To measure the concentration of carcinoembryonic antigen (CEA) in serial serum specimens of 47 healthy subjects and in serial sera of 59 patients with colorectal polyps of confirmed histology, obtained before or after (sometimes both) polypectomy, we used the Roche EIA and the Hybritech Tandem-E double monoclonal immunoenzymometric assays. Both methods gave comparable results for the healthy subjects but discordant values for some polyp patients. The Tandem-E test gave increased CEA results more frequently for two groups of polyp patients, the group of ex-smokers with neoplastic polyps (n = 14) and the group of smokers (n = 20). Smokers had significantly greater (P less than 0.025) mean concentrations of serum CEA than did nonsmokers, irrespective of whether they were healthy or had colorectal polyps. Smokers with recurrent polyps demonstrated significantly greater (P less than 0.050) mean concentrations of serum CEA than did smokers with a first occurrence of polyps. Polypectomy was followed by statistically significant decreases (P less than 0.050) of mean concentrations of serum CEA, primarily in polyp patients who were smokers. However, although CEA increases occurred frequently in polyp patients who smoked, these abnormalities did not fully correlate with polyp histology.

Adult↗
PubMed1989

Pancreatic oncofetal antigen and carbohydrate antigen 19-9 in sera of patients with cancer of the pancreas.

Pancreatic oncofetal antigen (POA) and carbohydrate antigen 19-9 (CA 19-9) were measured in the sera of 23 patients with cancer of the pancreas to determine the true positive rates of these cancer markers. In one group of unselected pancreatic cancer patients (n = 9), both tests showed above-normal results in three patients and both gave values that were within reference limits in three other patients. Two of the three remaining patients had increased CA 19-9 but normal POA values, and one patient had increased POA but normal CA 19-9 concentrations in serum. In another group of 14 pancreatic cancer patients, selected on the basis of increased concentrations of POA in serum, the CA 19-9 values were increased in eight. In four patients who had progressive disease, the concentrations of both markers increased with time in one patient, only POA in one, and only CA 19-9 concentration in another. (The fourth patient had increased but stable concentrations of POA and CA 19-9 in serum.) These data suggest that serum POA and CA 19-9 measurements should be used in combination in the evaluation of patients with cancer of the pancreas.

Adenocarcinoma↗
PubMed1989

Methods for determining "reference changes" from serial measurements: plasma lipid-bound sialic acid.

Lipid-bound sialic (neuraminic) acid (LSA) was measured in EDTA-treated plasma of 26 healthy subjects at three-month intervals for up to one year. The change in LSA concentration for consecutive measurements ranged from -54 to 42 mg/L (mean, -2.1 mg/L; SD, 19.6 mg/L; n = 56). The "reference change" for plasma LSA (+/- 2 SD), calculated from distribution of the differences, was +/- 39 mg/L. The 88th percentile of the intra-individual variance was 338 mg2/L2 and the mean variance was 159 mg2/L2. Using the homeostatic, autoregressive time-series model, a reference change of +/- 51 mg/L between two consecutive measurements was determined to be statistically significant (i.e., expected by chance no more than 5% of the time) in 88% of the healthy subjects. Only 73% of the healthy subjects would have had intra-individual variances corresponding to the reference change of +/- 39 mg/L according to the autoregressive model. The concentration of LSA in plasma was significantly decreased upon surgery in five of 10 patients with colorectal adenocarcinomas of Dukes stages A-C when we used +/- 39 mg/L as the reference change, but in only two of the 10 when we used +/- 51 mg/L as the reference change.

Adenocarcinoma↗
PubMed1987

A double-monoclonal immunoenzymometric assay for alpha 1-fetoprotein modified for increased analytical precision.

We modified a one-step, two-site, double monoclonal immunoenzymometric assay (Abbott Laboratories) for serum alpha1-fetoprotein (AFP) to increase its sensitivity and improve test precision at the low end. We increased sample size, incubation interval, and reaction time and temperature, and decreased the final reaction volume. Interassay CVs for the modified method ranged from 6.2 to 8.0% for mean concentrations of AFP in serum of 5.2 to 34.2 micrograms/L--substantially better than those for the unmodified monoclonal method--and agreed well with those of the comparison method (modified Abbott polyclonal immunoenzymometric assay). AFP values by the modified monoclonal procedure (y) correlated well with results by the polyclonal method (x): y = 0.983x + 1.84 micrograms/L (r = 0.927, n = 59). The detection limit of the modified monoclonal test was 0.2 microgram/L, as compared with 1.0 and 1.4 micrograms/L, respectively, for the modified polyclonal and the unmodified monoclonal procedures. We recommend using the modified monoclonal method for monitoring cancer patients with low tumor burden.

Antibodies, Monoclonal↗
PubMed1986

Formic and lactic acidosis in a fatal case of methanol intoxication.

A 33-year-old white man was admitted to the University of Utah Hospital after about 30 h of various symptoms, including blurred vision and (eventually) severe left flank and back pain. Upon admission, his serum pH was 6.80 and serum bicarbonate concentration (calculated from pCO2 and pH) was 3.9 mmol/L. The etiology for the acidosis became apparent 10 h after admission, when assay of the serum prepared from a blood specimen obtained at admission revealed a methanol concentration of 74 mmol/L (2.4 g/L). At this time the patient was placed on hemodialysis and intravenously infused with sodium bicarbonate. The methanol concentration in serum had decreased to 21 mmol/L 2 h later. Formate and lactate concentrations were, respectively, 10 and 23 mmol/L in serum sampled 4.5 h after hospitalization, at which time serum pH was 6.91 and bicarbonate concentration 7 mmol/L. The patient eventually died with extensive neuropathy.

Acid-Base Equilibrium↗
PubMed1985

A prospective study of myocardial damage in electrical injuries.

A prospective study was undertaken to determine the incidence of possible myocardial damage following electrical injury. Sixteen patients with non-flash electrical injuries were assessed utilizing serial electrocardiograms (ECG), creatine kinase (CK) and MB creatinine kinase (MB-CK) determinations, technetium 99m stannous pyrophosphate scans, and 24-hour Holter monitors. Results showed that five patients (31%) had abnormal ECG, nine patients (56%) had elevations of the MB-CK isoenzyme, and one patient had a transiently abnormal Holter monitoring. No patient had an abnormal technetium pyrophosphate cardiac scan. Of the nine patients with elevated MB-CK levels, only two had abnormal ECG. None of the patients had clinical evidence of cardiac dysfunction. These results indicate a poor correlation of elevated MB-CK levels with ECG abnormalities, and demonstrate a relatively low incidence of myocardial damage in association with electrical injuries.

Adolescent↗
PubMed1985

Effects of glycine on hemodynamic responses and visual evoked potentials in the dog.

To study the potential contribution of glycine toxicity in the transurethral resection syndrome, we evaluated hemodynamic and visual evoked potential responses to glycine infusion (1 g/kg) in 22 dogs anesthetized with halothane (1.0-1.2% end tidal. Three dogs received 5% glucose in normal saline without glycine; three received arginine (4 mg/kg) in normal saline without glycine; three received arginine (4 mg/kg) in normal saline without glycine; 10 received glycine (1 g/kg), then arginine (4 mg/kg) 120 min after the completion of glycine infusion; and six received arginine 30 min after the completion of glycine infusion. Arginine was infused to evaluate potential antagonistic effects of glycine toxicity. Blood levels of glycine, ammonia, arginine, urea, and formate were determined after infusions of glycine or arginine. All animals received about 5 ml X kg-1 X hr-1 of normal saline during the 2-4 hr of study. Immediately after glycine infusion, cardiac output increased 57%, whereas systemic vascular resistance and mean arterial pressure decreased 32% and 8%, respectively. Later cardiac output and mean arterial pressure were 41% and 18% less than control levels, whereas systemic vascular resistance returned to control levels. Both amplitude and latency of visual evoked potential waveforms were altered in the animals receiving glycine infusion but not in the control animals. These responses were associated with elevations of blood glycine (149 +/- 5 to 9591 +/- 809 microM/L, mean + SEM) and blood NH3 (10.5 +/- 2.8 to 100.0 +/- 13.6 microM/L), but not with formate levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗