Clinical Chemistry-Calculations, QC and Statistics Flashcards
- How many grams of sodium hydroxide (NaOH)
are required to prepare 150.0 mL of a 5.0% w/v
solution?
A. 1.5 g
B. 4.0 g
C. 7.5 g
D. 15.0 g
C. 7.5 g
- How many milliliters of glacial acetic acid are
needed to prepare 2.0 L of 10.0% v/v acetic acid?
A. 10.0 mL
B. 20.0 mL
C. 100.0 mL
D. 200.0 mL
D. 200.0 mL
- A biuret reagent requires preparation of a stock
solution containing 9.6 g of copper II sulfate
(CuSO4) per liter. How many grams of CuSO4* 5H2O are needed to prepare 1.0 L of the stock
solution?
Atomic weights: H = 1.0; Cu = 63.6; O = 16.0; S = 32.1
A. 5.4 g
B. 6.1 g
C. 15.0 g
D. 17.0 g
C. 15.0 g
- How many milliliters of HNO3 (purity 68.0%,
specific gravity 1.42) are needed to prepare 1.0 L
of a 2.0 N solution?
Atomic weights: H = 1.0; N = 14.0; O = 16.0
A. 89.5 mL
B. 126.0 mL
C. 130.5 mL
D. 180.0 mL
C. 130.5 mL
- Convert 10.0 mg/dL calcium (atomic weight = 40.1)
to International System of Units (SI).
A. 0.25
B. 0.40
C. 2.5
D. 0.4
C. 2.5
- Convert 2.0 mEq/L magnesium (atomic
weight = 24.3) to milligrams per deciliter.
A. 0.8 mg/dL
B. 1.2 mg/dL
C. 2.4 mg/dL
D. 4.9 mg/dL
C. 2.4 mg/dL
- How many milliliters of a 2,000.0 mg/dL glucose
stock solution are needed to prepare 100.0 mL of a
150.0 mg/dL glucose working standard?
A. 1.5 mL
B. 7.5 mL
C. 15.0 mL
D. 25.0 mL
B. 7.5 mL
- What is the pH of a solution of HNO3, if the
hydrogen ion concentration is 2.5 × 10–2 M?
A. 1.0
B. 1.6
C. 2.5
D. 2.8
B. 1.6
- Calculate the pH of a solution of 1.5 × 10–5 M
NH4OH.
A. 4.2
B. 7.2
C. 9.2
D. 11.2
C. 9.2
- How many significant figures should be reported
when the pH of a 0.060 M solution of nitric acid
is calculated?
A. 1
B. 2
C. 3
D. 4
B. 2
- What is the pH of a 0.05 M solution of acetic
acid? Ka = 1.75 × 10–5, pKa = 4.76
A. 1.7
B. 3.0
C. 4.3
D. 4.6
B. 3.0
- What is the pH of a buffer containing 40.0 mmol/L
NaHC2O4 and 4.0 mmol/L H2C2O4? (pKa = 1.25)
A. 1.35
B. 2.25
C. 5.75
D. 6.12
B. 2.25
- A solvent needed for HPLC requires a 20.0 mmol/L phosphoric acid buffer, pH 3.50, made by mixing KH2PO4 and H3PO4. How many grams of
KH2PO4 are required to make 1.0 L of this
buffer?
Formula weights: KH2PO4 = 136.1; H3PO4 = 98.0;
pKa H3PO4 = 2.12
A. 1.96 g
B. 2.61 g
C. 2.72 g
D. 19.2 g
B. 2.61 g
- A procedure for cholesterol is calibrated with
a serum-based cholesterol standard that was
determined by the Abell–Kendall method to
be 200.0 mg/dL. Assuming the same volume
of sample and reagent are used, calculate the
cholesterol concentration in the patient’s sample from the following results.
A. 123 mg/dL
B. 172 mg/dL
C. 232 mg/dL
D. 314 mg/dL
B. 172 mg/dL
- A glycerol kinase method for triglyceride calls for a
serum blank in which normal saline is substituted
for lipase in order to measure endogenous glycerol.
Given the following results, and assuming the
same volume of sample and reagent are used for
each test, calculate the triglyceride concentration
in the patient’s sample.
A. 119 mg/dL
B. 131 mg/dL
C. 156 mg/dL
D. 180 mg/dL
B. 131 mg/dL
- A procedure for aspartate aminotransferase (AST)
is performed manually because of a repeating error
code for nonlinearity obtained on the laboratory’s
automated chemistry analyzer; 0.05 mL of serum
and 1.0 mL of substrate are used. The reaction rate
is measured at 30°C at 340 nm using a 1.0 cM
light path, and the delta absorbance (-ΔA) per
minute is determined to be 0.382. Based upon a
molar absorptivity coefficient for NADH at
340 nm of 6.22 X 103 M–1 cM–1 L–1, calculate
the enzyme activity in international units (IUs)
per liter.
A. 26 IU/L
B. 326 IU/L
C. 1228 IU/L
D. 1290 IU/L
D. 1290 IU/L
- When referring to quality control (QC) results,
what parameter usually determines the acceptable
range?
A. The 95% confidence interval for the mean
B. The range that includes 50% of the results
C. The central 68% of results
D. The range encompassed by ±2.5 standard
deviations
A. The 95% confidence interval for the mean
- Which of the following quality control (QC) rules
would be broken 1 out of 20 times by chance alone?
A. 1_2s
B. 2_2s
C. 1_3s
D. 1_4s
A. 1_2s
- Which of the following conditions is cause for
rejecting an analytical run?
A. Two consecutive controls greater than 2 s above
or below the mean
B. Three consecutive controls greater than 1 s above
the mean
C. Four controls steadily increasing in value but less
than ±1 s from the mean
D. One control above +1 s and the other below –1 s
from the mean
A. Two consecutive controls greater than 2 s above
or below the mean
- One of two controls within a run is above +2s
and the other control is below –2s from the mean.
What do these results indicate?
A. Poor precision has led to random error (RE)
B. A systematic error (SE) is present
C. Proportional error is present
D. QC material is contaminated
A. Poor precision has led to random error (RE)
- Two consecutive controls are both beyond –2s
from the mean. How frequently would this occur
on the basis of chance alone?
A. 1:100
B. 5:100
C. 1:400
D. 1:1,600
D. 1:1,600
- The term R4S means that:
A. Four consecutive controls are greater than ±1
standard deviation from the mean
B. Two controls in the same run are greater than
4s units apart
C. Two consecutive controls in the same run are
each greater than ±4s from the mean
D. There is a shift above the mean for four
consecutive controls
B. Two controls in the same run are greater than
4s units apart
- Which of the following assays has the poorest
precision?
A.
- Given the following data, calculate the coefficient
of variation for glucose.
A. 3.0%
B. 4.6%
C. 7.6%
D. 33.0%
A. 3.0%
- Examine the Levy–Jennings chart at the bottom of the previous page and identify the QC problem
that occurred during the first half of the month.
A. Shift
B. Trend
C. Random error
D. Kurtosis
B. Trend
- Referring to the Levy–Jennings chart, what is the
first day in the month when the run should be
rejected and patient results should be repeated?
A. Day 6
B. Day 7
C. Day 8
D. Day 9
C. Day 8
- Referring to the Levy–Jennings chart, what
analytical error is present during the second
half of the month?
A. Shift
B. Trend
C. Random error
D. Kurtosis
A. Shift
- Given the following QC chart, identify the day in
which a violation of the R4s QC rule occurs.
A. Day 3
B. Day 8
C. Day 10
D. Day 15
D. Day 15
- Two freezing point osmometers are compared by running 40 paired patient samples one time on
each instrument, and the following results are
obtained:
If the critical value for F = 2.8, then what
conclusion can be drawn regarding the
precision of the two instruments?
A. There is no statistically significant difference in
precision
B. Osmometer A demonstrates better precision that
is statistically significant
C. Osmometer B demonstrates better precision that
is statistically significant
D. Precision cannot be evaluated statistically when
single measurements are made on samples
A. There is no statistically significant difference in
precision
- Two methods for total cholesterol are compared
by running 40 paired patient samples in duplicate
on each instrument. The following results are
obtained:
Assuming the samples are collected and stored
in the same way and the analysis done by a
technologist who is familiar with both methods,
what is the bias of method y?
A. 0.4
B. 7.2
C. 10.6
D. 11.0
D. 11.0
- Which explanation is the best interpretation of the
following BUN bias plot?
A. The new method consistently overestimates the
BUN by a constant concentration
B. The new method is greater than the reference
method but not by a statistically significant
margin
C. The new method is lower than the reference
method by 5 mg/dL
D. The new method is lower than the reference and
the magnitude is concentration dependent
D. The new method is lower than the reference and
the magnitude is concentration dependent
- Serum samples collected from hospitalized patients
over a 2-week period are split into two aliquots
and analyzed for prostate specific antigen (PSA)
by two methods. Each sample was assayed by both
methods within 30 minutes of collection by a
technologist familiar with both methods. The
reference method is method × (upper reference
limit = 4.0 μg/L). Linear regression analysis was
performed by the least-squares method, and results
are as follows:
Which statement best characterizes the
relationship between the methods?
A. There is a significant bias caused by constant
error
B. There is a significant proportional error
C. There is no disagreement between the methods
because the correlation coefficient approaches 1.0
D. There is no systematic error, but the random
error of the new method is unacceptable
A. There is a significant bias caused by constant
error
- Which statement best summarizes the relationship
between the new BUN method and reference
method based upon the following linear regression
scatterplot?
A. The methods agree very well but show a high
standard error of estimate
B. There is little or no constant error, but some
proportional error
C. There will be a significant degree of uncertainty
in the regression equation
D. There is significant constant and proportional
error but little random error
B. There is little or no constant error, but some
proportional error
- A new method for BUN is evaluated by comparing
the results of 40 paired patient samples to the
urease-UV method. Normal and high controls
were run on each shift for 5 days, five times per
day. The results are as follows:
What is the total analytical error estimate for a
sample having a concentration of 50 mg/dL?
A. –2.2 mg/dL
B. –2.8 mg/dL
C. –7.5 mg/dL
D. –10.0 mg/dL
C. –7.5 mg/dL
- The following plot represents a study of a
screening test for malignant prostate cancer using
plasma PSA (ng/mL). The outcome measured
was positive cytology results obtained by biopsy.
What concentration gives the highest sensitivity with the last number of unnecessary biopsies ?
A. 2.6
B. 3.6
C. 3.8
D. 5.2
B. 3.6
