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At least 1,261 records · Page 70Linked to original sources
PubMedDate not supplied

Aminoglycoside serum concentration sampling via central venous catheters: a potential source of clinical error.

Two patients receiving aminoglycosides via central venous Silastic catheters were noted to have serum drug concentrations markedly divergent from expected results. Study of these patients, and of four additional patients prospectively selected for study, demonstrated that three of five patients had higher peak and/or trough aminoglycoside serum concentrations--when blood was obtained from the central venous catheter--than were contained in simultaneous samples from peripheral blood; these divergent results were noted after the catheter had been in use for more than 1 week; divergent results were not improved by additional catheter flushing prior to central venous blood sampling. These observations suggest that spurious aminoglycoside serum concentration results may sometimes be obtained when blood sampling is performed from central venous Silastic catheters, and can result in improper drug dosage alterations. It is necessary to access the timing, processing, and reliability of serum drug-monitoring practices on a routine basis to preclude such problems, and to reassess individual patient-monitoring studies which are inconsistent with anticipated results.

Adult↗
PubMed2003

Computer decision support as a source of interpretation error: the case of electrocardiograms.

OBJECTIVE: The aim of this study was to determine the effect that the computer interpretation (CI) of electrocardiograms (EKGs) has on the accuracy of resident (noncardiologist) physicians reading EKGs. DESIGN: A randomized, controlled trial was conducted in a laboratory setting from February through June 2001, using a two-period crossover design with matched pairs of subjects randomly assigned to sequencing groups. MEASUREMENTS: Subjects' interpretive accuracy of discrete, cardiologist-determined EKG findings were measured as judged by a board-certified internist. RESULTS: Without the CI, subjects interpreted 48.9% (95% confidence interval, 45.0% to 52.8%) of the findings correctly. With the CI, subjects interpreted 55.4% (51.9% to 58.9%) correctly (p < 0.0001). When the CIs that agreed with the gold standard (Correct CIs) were not included, 53.1% (47.7% to 58.5%) of the findings were interpreted correctly. When the correct CI was included, accuracy increased to 68.1% (63.2% to 72.7%; p < 0.0001). When computer advice that did not agree with the gold standard (Incorrect CI) was not provided to the subjects, 56.7% (48.5% to 64.5%) of findings were interpreted correctly. Accuracy dropped to 48.3% (40.4% to 56.4%) when the incorrect computer advice was provided (p = 0.131). Subjects erroneously agreed with the incorrect CI more often when it was presented with the EKG 67.7% (57.2% to 76.7%) than when it was not 34.6% (23.8% to 47.3%; p < 0.0001). CONCLUSIONS: Computer decision support systems can generally improve the interpretive accuracy of internal medicine residents in reading EKGs. However, subjects were influenced significantly by incorrect advice, which tempers the overall usefulness of computer-generated advice in this and perhaps other areas.

Cross-Over Studies↗
PubMed1978

Subhourly variability of circulating third trimester maternal steroid concentrations as a source of sampling error.

Seven plasma samples from five normal third trimester pregnant women, drawn every 5 and 15 min at similar times on 2 days, 2 days apart, were measured in quadruplicate for estradiol (E2), estriol, progesterone, 16 alpha-hydroxyprogesterone, and 17 alpha-hydroxyprogesterone (17P). The mean of the 22 samples obtained from each subject for each steroid was used as a reference mean. Individual determinations were converted to percentages of the reference mean which was normalized to 0%. All pregnancies were uncomplicated, and all mean values were within the normal range for gestational age. Variability about the reference mean for single samples, however, range from a low of -80% to a high of 150%. The single sample, 95% confidence intervals for individual steroids pooled from the five subjects (110 determinations) range from +/- 36% (E2) to +/- 60% (17P). Mean percentage coefficients of variation between 5-min and 15-min sampling sequences were compared by analysis of variance. There is no significant difference between the mean percentage coefficients of variation of a 5-min as opposed to a 15-min sampling sequence for any of the hormones measured. The 95% confidence interval width around the reference mean is a function of the number of samples obtained. Because the 95% confidence interval width from 110 measurements decreases approximately as 1/ square root n with increasing sampling size, the decrement progressively diminishes. For E2, the least variable steroid, a one-sample 95% confidence interval width of +/- 36% decreases to approximately +/- 18% with four samples or approximately +/- 12% with nine samples. For 17P, the most variable steroid, a one-sample 95% confidence interval width of +/- 60% decreases to approximately +/- 30% with four samples or approximately +/- 20% with nine samples. Multiple sampling with plasma pooling is required for the accurate study of steroid concentrations in individual subjects in late pregnancy.

17-alpha-Hydroxyprogesterone↗
PubMed2005

Mood, dissociation and false memories using the Deese-Roediger-McDermott procedure.

Who is likely to have a false memory? Does being in a certain transient state, such as a negative mood, mean that a person is more like to have a false memory? These important questions are examined using the Deese-Roediger-McDermott (DRM) procedure. The amount of false memories was compared with people's score on a dissociation measure and by mood. Unlike past research, which has used different procedures to explore false memories, we found that dissociation was not associated with false memories. We argue that this is because the DRM procedure requires two processes for a false memory (the generation of the critical lure and mistaking its source), while most false memory procedures only require one process (source monitoring error) because the errant information is suggested to the participant. This pattern of results suggests that only errors with the source monitoring process are associated with dissociation. We found that mood was related to false memories, but it was dependent on the specific task demands. If participants were told to recall as many words as they could, then people in a negative mood had more false memories. However, if they were told to recall as many words as they felt like recalling, then there were more false memories for people in a positive mood. This can be explained by the mood-as-input hypothesis. Results are discussed in relation to both theories and applications of memory.

Acoustic Stimulation↗
PubMed1981

Pneumocystis infection masquerading as diffuse alveolar damage: a potential source of diagnostic error.

The nonspecific histopathologic changes of diffuse alveolar damage (DAD) were the only findings in nine of 17 lung biopsy specimens containing Pneumocystis carinii infection. Because of the frequent absence of the classically described intra-alveolar frothy material, special stains for organisms should be performed on all biopsy specimens from immunocompromised patients that show DAD, and the diagnosis of Pneumocystis infection should not be discarded unless careful search for organisms using special stains is negative.

Adult↗
PubMed1998

Determination of pH in human erythrocytes. Sources of systematic error.

The results of a simultaneous determination of the pH value in erythrocytes with the potentiometric measuring method and the 14C-labelled 5,5-dimethyl-2,4-oxazolidinedione (DMO) method showed a mean method difference of 0.026 pH units. The cause of this discrepancy was assumed to be matrix-inherent liquid-junction potentials in the potentiometric measurement. Taking these into account in the calculation leads to consistent values for the methods investigated. The DMO method proved to be free of systematic errors. Another indication of this is that its mean ratio of extracellular to intracellular H+ ion concentration (H+e/H+i) substantially agreed with the distribution ratios of other freely diffusible ions and their pH dependence.

Erythrocytes↗
PubMedDate not supplied

A noncontact sensor for measurement of distal residual-limb position during walking.

A simple noncontact device was implemented for measuring the position of the distal residual limb relative to the prosthetic socket during ambulation. The device was a small and lightweight photoelectric sensor positioned within a frame mounted immediately beneath the socket. Calibration tests showed that the sensor had a displacement range of 60.0 mm. The root-mean-square error for all sources of error considered (different reflective surfaces, peak-to-peak signal noise, drift, nonlinearity, different surface tilt angles, surface curvature, and wetness [simulating sweating]) was <1.95% full-scale output. We used the sensor in a preliminary study on a unilateral, transtibial amputee with diabetes to assess pistoning during ambulation. Results showed an average 41.7 mm proximal displacement during swing phase relative to stance phase. When the subject was walking on a flat surface, pistoning was significantly less (p = 0.000) with a supracondylar strap compared with no supracondylar strap, although the difference was not substantial (0.8 mm). A 5 min rest period caused the limb to displace proximally in the socket approximately 4.8 mm during subsequent walking trials, possibly reflecting limb enlargement and thus a more proximal position in the socket after the rest period. The device can potentially be used in prosthetics research for evaluating clinical features that may affect limb position and pistoning and thus fit.

Amputation Stumps↗
PubMed2002

Whole-blood glucose testing at alternate sites: glucose values and hematocrit of capillary blood drawn from fingertip and forearm.

OBJECTIVE: To measure hematocrit (Hct) and glucose concentration in capillary blood drawn from the fingertip and forearm of a group of 50 nonfasting subjects with diabetes. RESEARCH DESIGN AND METHODS: Hct was determined indirectly by measuring Hb with the HemoCue B-Hemoglobin Photometer. Glucose was assayed with the HemoCue B-Glucose Analyzer, chosen as the independent control assay, and the Sof-Tact Blood Glucose System. Testing session with each subject lasted approximately 30 min and consisted of a sequence of tests with each device (SofTact, HemoCue Glucose, and HemoCue Hemoglobin), performed on the arm and then on the fingertip. This sequence was performed three times, so all tests were done in triplicate. Additional fingersticks were performed on each subject at the start and end of the session to measure net change of glucose status during the experiment with a YSI Glucose Analyzer. The mean of the triplicate assays was used to calculate each subject's percent of glucose difference between arm and finger [(arm glucose - finger glucose)/finger glucose]. Because of the order in which replicates were performed, time-dependent changes in the glucose status of subjects had little effect on the mean values. Thus, the percent of glucose difference calculated herein reflects the intrinsic difference between forearm and fingertip. RESULTS: Hb concentration and Hct were found to be significantly higher in the arm than in the finger. When intraperson differences were calculated, the difference for Hb and Hct was found to be 1.8 +/- 1.1 g/dl (mean +/- SD) and 5.3 +/- 3.0%, respectively. In contrast to Hb, the percent of glucose difference between arm and finger was statistically insignificant. When measured with HemoCue, the percent of glucose difference was -0.1 +/- 8% for all 50 subjects, -1 +/- 6% for 20 subjects, for whom blood glucose varied <9 mg/dl during the experiment, and 2 +/- 10% for 15 subjects, for whom blood glucose varied >18 mg/dl. Thus, irrespective of how much blood glucose changed among the subjects, the glucose difference between forearm and fingertip was insignificant and less than measurement errors. A major source of error in the calculated differences was variability between replicates. No correlation was observed between an individual's Hct bias and his or her percent of glucose difference, as measured with HemoCue. The results with Sof-Tact were similar, with percent of glucose difference again being statistically insignificant. The measured difference was -4 +/- 13% for all 50 subjects, -1 +/- 15% for 20 subjects, for whom blood glucose varied <9 mg/dl during the experiment, and -1 +/- 12% for 15 subjects, for whom blood glucose varied >18 mg/dl. There was no correlation between a subject's Hct bias and his or her glucose difference, as measured with Sof-Tact. CONCLUSIONS: In this cross-sectional study of 50 nonfasting subjects whose blood glucose concentration changed to various degrees during the experiment, no significant glucose difference was observed between the capillary beds of the forearm and fingertip, regardless of whether glucose was assayed with HemoCue or the Sof-Tact Blood Glucose System. On the other hand, Hb concentration and Hct were found to be significantly higher in the capillary blood of the forearm.

Adolescent↗
PubMed1986

Decalcification of schistosome eggs during staining of tissue sections: a potential source of diagnostic error.

Miracidial nuclei within calcified schistosome eggs are frequently mummified. Calcified eggs are often decalcified prior to or during the routine processing and staining of tissues, and mummified miracidial nuclei then stain clearly and are often arranged in the patterns seen in live eggs. These miracidia may be incorrectly assumed to be alive or to have died recently and thus be taken as evidence of an active infection requiring chemotherapy. The present observations demonstrate the decalcification of mineralized eggs by hematoxylin preparations used for routine staining of tissue sections.

Adult↗