Part 1

Foundations

Build reliable bench habits: check specimens, calculate dilutions and test performance, review controls, work safely, and report and correct results.

Steps

Dilution factors and patient results12 min · Calculate a dilution factor and specimen fraction from prepared volumes · Calculate the original concentration from a diluted measurement
Making a dilution and checking the reading13 min · Calculate the specimen and diluent volumes for a chosen dilution · Decide whether a diluted reading falls inside the measuring interval before reporting
Serial dilutions14 min · Calculate a cumulative dilution factor · Calculate the destination concentration in a serial dilution step · Predict how a transfer or diluent volume error changes a serial dilution
Aliquots, withdrawal and mixing12 min · Calculate the amount of solute in an aliquot · Predict the concentration after withdrawing a well-mixed aliquot · Mix a dilution before transferring the next aliquot
The testing cycle and patient identity12 min · Locate an error in the preanalytic, analytic, or postanalytic phase · Verify patient and specimen identity before testing or giving a result
Is the specimen fit to test?15 min · Decide whether a clot, short fill, wrong tube, or delay makes a specimen unsuitable · Recognize high potassium with low calcium as a sign of EDTA carryover · Recognize when fluid from an infusion line has diluted or spiked the specimen
Hemolysis, interference and delta checks15 min · Distinguish collection hemolysis from possible hemolysis in the patient · Distinguish a patient-related interference from a collection problem · Check identity, contamination, and the run behind a failed delta check before release
Releasing, calling and correcting results15 min · Choose release, repeat, comment, or recollection from the specimen checks and QC · Communicate a critical result with identifiers, units, and confirmed receipt · Call an established critical result before continuing routine work · Correct a reported error, keep both reports, and notify the care team
Control statistics13 min · Calculate the mean of control measurements · Calculate standard deviation from stated control limits and state its unit · Calculate coefficient of variation from a mean and standard deviation · State the share of control results expected within 1, 2, and 3 SD of the mean
Reading a Levey-Jennings chart14 min · Recognize a shift, trend, or random scatter on a Levey-Jennings chart · Tell a 1-2s warning from a 1-3s rejection · Tell a 2-2s violation from a 1-3s violation · Tell a 2-2s violation from a 4-1s violation
R-4s, 10x and finding the cause14 min · Recognize an R-4s violation within one run · Recognize a 10x violation in consecutive same-side controls · Match a QC shift, trend, or random error to its likely causes
After QC fails14 min · Confirm corrective action before accepting the next QC run · Decide which patient results need review after rejected QC · Set a new control lot's mean from its crossover runs and its SD from the established CV
How well a method performs14 min · Calculate a sigma metric with compatible error, bias, and imprecision units · Tell method agreement from a high correlation coefficient · Test proficiency samples through the routine patient workflow
Point-of-care testing and shipping specimens14 min · Check operator, reagent, device, and control readiness before point-of-care testing · Match a test's CLIA complexity to the certificate that covers it · Choose safe packaging and handling for a specimen shipment
Protection, exposures, spills and fire15 min · Choose PPE and handling controls for a task's splash, sharps, or aerosol risk · Choose the immediate response to a blood or body-fluid exposure · Use the SDS and hazard label to choose chemical handling and spill precautions · Choose the required response to a fire or equipment emergency
Making up solutions15 min · Calculate molarity or reagent mass using the solute molar mass · Calculate normality for the stated reaction · Calculate a percent solution on its stated mass/volume, volume/volume, or mass/mass basis · Calculate the stock volume required for a target solution
Unit conversions, the median and absorbance13 min · Convert between compatible mass, volume, and amount concentration units · Calculate the median of an ordered set of results · Convert percent transmittance to absorbance
Sensitivity, specificity and predictive values14 min · Calculate diagnostic sensitivity against the reference classification · Calculate diagnostic specificity against the reference classification · Calculate positive and negative predictive values
Iron-binding capacity and transferrin saturation13 min · Calculate TIBC from transferrin using the procedure's factor and units · Calculate TIBC or UIBC from the other iron-capacity measurements · Calculate transferrin saturation from serum iron and TIBC
Globulin, indirect bilirubin and LDL cholesterol14 min · Calculate globulin and the albumin/globulin ratio · Calculate the indirect bilirubin fraction from total and direct results · Calculate non-HDL cholesterol from total and HDL cholesterol · Calculate Friedewald LDL cholesterol in mg/dL or mmol/L

What you'll be able to do

The testing cycle

Locate an error in the preanalytic, analytic, or postanalytic phase

Ordering, identification, and acceptability

Specimen integrity and interference

Statistical control of a measurement procedure

Oversight of a distributed testing program

Biological hazard controls

Parts and dilution factor

Molarity

In the lab

Morning chemistry runAbout 20 to 30 minutes Try this at the Dilution stationPendingCK · U/L>1000UNDILUTED · ABOVE AMR1:5 to 500 µLDilute specimen Try this at the Dilution stationPendingCK · U/L>1000UNDILUTED · ABOVE AMR1:8 to 800 µLDilute specimen Try this at the Dilution stationPendingOriginal · mg/L100Source concentrationUnequal steps: 2, 5, 10Dilute specimen Try this at the Dilution stationPendingOriginal · mg/L100Source concentrationThree twofold stepsDilute specimen

10 more at the stations

Try this at the Chemistry stationPendingResult pending review1AWAITING VERIFICATIONHemolysis: decide assay by assayReview results Try this at the QC workstationPendingQC run due07:00READY TO REVIEWCase 06Review QC Try this at the QC workstationPendingQC run due07:00READY TO REVIEWCase 04Review QC Try this at the QC workstationPendingQC run due07:00READY TO REVIEWCase 05Review QC Try this at The phonePendingShift 1Start shift Try this at The phonePendingShift 3Start shift Try this at the QC workstationPendingSodium above the meanReview QC Try this at the QC workstationPendingAST warning resultReview QC Try this at the QC workstationPendingBoth calcium levels highReview QC Try this at the Dilution stationPendingOriginal · mg/L100Source concentrationThree tenfold stepsDilute specimen

On paper

Calculations and Reference Ranges, quick reference 1 of 10
01 / 10 · Calculations and Reference Ranges
Dilutions and dilution factors
Parts, volumes, serial steps, and the reported result
Adding diluent lowers concentration. The dilution factor (DF) is the final volume divided by the specimen volume. A DF of 5 gives one fifth of the original concentration.
Example: 1:5 dilution
Here, 1:5 means specimen:final volume: one specimen part plus four diluent parts. A written 1 + 5 makes six parts, DF = 6.
Specimen
100 µL
Diluent
100 µL
Diluent
100 µL
Diluent
100 µL
Diluent
100 µL
500 µL final volume = 100 µL specimen + 400 µL diluent.
Equal-volume schematic. µL = microliter.
Calculating the dilution factor
Formula
DF = final volume ÷ specimen volume
In the 1:5 example
Final volume = 500 µL
Specimen volume = 100 µL
DF = 500 ÷ 100 = 5
Volumes and factor
Specimen volume
Final volume ÷ DF
Diluent volume
Final − specimen volume
Prepare 1:10, final 1.0 mL.
Specimen = 1.0 ÷ 10 = 0.10 mL.
Diluent = 1.0 − 0.10 = 0.90 mL.
mL = milliliter. 1 mL = 1,000 µL.
Concentration and result
Diluted concentration
Original concentration ÷ DF
Original concentration
Diluted concentration × DF
A 1:5 aliquot measures 84 U/L.
84 × 5 = 420 U/L in the original specimen. U/L = units per liter.
Apply the factor once: an analyzer-corrected 420 U/L stays 420 U/L. Use the method's diluent and validated measuring range.
Cumulative dilution factor
Original specimen
1:5 step
Total DF = 5
1:4 step from that mixture
Total DF = 5 × 4 = 20
Each step dilutes the well-mixed solution from the preceding tube, so the cumulative dilution factor is the product of the step factors. A result of 12 mg/dL in the second tube gives 12 × 20 = 240 mg/dL in the original specimen. mg/dL = milligrams per deciliter.
https://latticemls.org/guides/dilutions/ · Sources checked September 5, 2026 · vc32c65d9
© LatticeMLS · CC BY-NC-SA 4.0
Calculations and Reference Ranges01 / 10Dilutions and dilution factorsParts, volumes, serial steps, and the reported result
Laboratory Operations, quick reference 2 of 10
02 / 10 · Laboratory Operations
Common QC rule violations
Six statistical rules and the limits of their interpretation
Quality control (QC) compares a control result with its established mean and standard deviation (SD), a measure of usual variation. Random error widens the scatter around the mean. Systematic error moves results toward one side of it. The patterns below suggest which type to investigate.
Vertical position = (result − mean) ÷ SD, using each level's own target. Lines: mean (0), ±1, ±2, ±3 SD. A square marks each result that meets the named rule.
1_2s
One result beyond ±2 SD.
In the classic scheme this is a warning. Check the selected rejection rules.
1_3s
One result beyond ±3 SD.
Reject the run and investigate possible random or systematic error.
2_2s
Two consecutive beyond the same 2 SD limit.
Reject the run and investigate possible systematic error.
R_4s
One > +2 SD, one < −2 SD, in one run.
The 4.8 SD spread in this example requires rejection and suggests random error.
4_1s
Four consecutive beyond the same 1 SD limit.
Reject the run and investigate possible systematic error.
10_x
Ten consecutive on one side of the mean.
Reject the run and investigate possible systematic error.
Examples use one level across runs, except R_4s (two levels, one run). The 2_2s rule also applies across levels within a run. The 4_1s and 10_x rules can span levels and runs as the QC plan specifies.
Warning and rejection
In the classic Westgard scheme, 1_2s is a warning to check the rejection rules. Plans that evaluate every rule directly can detect the 4_1s and 10_x examples here even though no result exceeds 2 SD.
Respond to a rejection
Stop reporting affected patient results. Use the adopted QC plan to investigate controls, reagents, calibration, and instrument performance. After correction and acceptable QC, assess which patient results need review or repeat testing. A passing repeat alone does not explain the original failure.
https://latticemls.org/guides/quality-control/ · Sources checked September 5, 2026 · v516bfe5c
© LatticeMLS · CC BY-NC-SA 4.0
Laboratory Operations02 / 10Common QC rule violationsSix statistical rules and the limits of their interpretation

08 / 10 · Laboratory Operations

Hemolysis, lipemia, and icterus

Appearance and interference in serum or plasma

Hemolysis, lipemia, and icterus can alter serum or plasma measurements. The same specimen may be acceptable for one test and unsuitable for another because each method responds differently to interference.

Hemolysis
Pink to red from free hemoglobin

Lipemia
Cloudy to milky from lipid particles

Icterus
Deep yellow to brown from bilirubin

Appearance schematics. Clear serum/plasma is usually pale yellow. Mixed interferences can obscure the appearance. A visual estimate cannot decide whether a specimen is acceptable.

Normal

Hemolyzed

Lipemic

Icteric

Finding	How results may change	Practical implication
Hemolysis	Cell rupture releases potassium and lactate dehydrogenase. Free hemoglobin absorbs light and can affect chemical reactions.	Potassium released from the red cells raises the potassium result. The size and direction of other biases vary by analyte and method. Recollection may resolve collection damage. Hemolysis that occurred in the patient may persist after recollection.
Lipemia	Particles scatter light and affect sampling. Reduced plasma-water fraction affects methods that dilute the sample.	Indirect ion-selective electrodes can report falsely low sodium. Direct electrodes generally avoid this water-fraction effect. Lipid removal may also remove analyte.
Icterus	Bilirubin absorbs light and can react with assay components, including oxidants.	Effects differ between assays. A fresh draw may still be icteric, so an alternate validated method may be needed.

What the interference index means

An instrument interference index estimates hemoglobin, bilirubin, or turbidity from optical readings. Its scale comes from the instrument method and cannot be inferred from color alone. A lipemia index measures turbidity and gives no triglyceride concentration. Each platform has its own index scale and limits.

Review each affected test

Compare the index with the manufacturer's interference data and the laboratory's verified limit for that test. Suppress, qualify, recollect, or use a validated alternate method as the procedure directs. A patient specimen can be affected even when controls pass.

Laboratory Operations08 / 10Hemolysis, lipemia, and icterusAppearance and interference in serum or plasma

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Foundations

Steps

What you'll be able to do

The testing cycle

Ordering, identification, and acceptability

Specimen integrity and interference

Statistical control of a measurement procedure

Oversight of a distributed testing program

Biological hazard controls

Parts and dilution factor

Molarity

Dilutions and dilution factors

Example: 1:5 dilution

Calculating the dilution factor

Volumes and factor

Concentration and result

Cumulative dilution factor

Common QC rule violations

1_2s

1_3s

2_2s

R_4s

4_1s

10_x

Warning and rejection

Respond to a rejection

Hemolysis, lipemia, and icterus

What the interference index means

Review each affected test