Fundamentals of Lab medicine-part 1 W2:L2

MLT Job Settings:

-Hospitals
-Private laboratories
-Community health clinics
-Public health facilities
-IT, other areas w/in the hospital
-University research labs
-Biotechnology companies
-Specialty labs, e.g. in vitro fertilization labs
-Armed Forces
-Teaching

Laboratory Director/Pathologist

All licensed laboratories must operate under the direction of a Pathologist

Anatomic Pathologist:

Physician with 4-5 years of training in the examination of surgically removed specimens

Clinical Pathologist:

Physician with training in clinical pathology or laboratory medicine

Laboratory Manager/Supervisor:

Responsible for the technical aspects in
the laboratory and day-to-day
operations

Medical Laboratory Technologist (MLT):

Performs general duty laboratory testing

Why order a lab test?

-Diagnosis of disease
-Management of illness of health
-Predict patient prognosis
-Establish a baseline
-Screen for “hidden” disease (no symptoms)

~85% of physician decisions and diagnosis are based
on laboratory test results

OBJECTIVES:

To define as objectively as possible health and disease*
To help predict the course of a disease
To monitor the effectiveness of treatment
To seek for underlying causes of disease

Morbidity:

Decreased life expectancy

How are Lab Tests ordered?

Electronic entry:
-hospital Information System (HIS)
-Laboratory Information System (LIS)

“Manual” Ordering:
-Requisitions: paper lab order forms
-Provincial order forms (OHIP form)

Laboratory Requisition Requirements:

Full name of patient

Patient unique number:
-“Admission” numbers: Every time a patient is registered into the
HIS/LIS a unique admission number is generated which identifies
that patient (for that admission)

Patient demographics: sex, DOB, address, etc

Order info: date, time, patient location, primary care provider

Tests ordered and priority: stat, urgent, routine

Relevant patient information: height/weight, drugs in use, race, disorder/disease

Collection info: date, time, collected by, fasting, patient
temp

Accessioning:

The act of logging in/documenting the receipt of a specimen in the lab

-INFO documented: date/time specimens received in the lab, received by
-Generates an accession number:
Every UNIQUE specimen has a unique specimen/sample ID number

How do we report results?

Interface: Electronic automatic transfer of results from the analyzer to LIS

What’s on the Lab Report?

Test info:
(date/time /person verifying results)

Test results :
-Test units, reference intervals, critical values
-Sample comments, interpretative comments
-Phoned results (what, to whom, by whom)

Are all lab orders the same?

No! The Lab can receive tests orders
in different ways:

Reference Intervals :

“Normal Values”: a range of values obtained by measurement of a particular type of quantity on a reference individual = usual values for a healthy population.

-Positive Diagnosis (“Rule-in”): condition (lab results) that resembles that typical of a particular disease.

-Diagnosis by Exclusion (“Rule-Out”): observations (lab results) that do not fit patterns characteristic of alternative diseases.

IFCC (International Federation of Clinical Chemistry)

Each lab must establish their own Reference Intervals!!!

recommends “reference interval” and 5 factors specified when establishing a RI

5 factors specified when establishing a RI:

1.Define demographics: age, sex, race, pregnancy
2. Criteria for inclusion and exclusion of data
3. Physiological & environment conditions under which samples are collected (date/time/food intake/smoking...)
4. Specimen collection procedure
5. Analytical method used including accuracy and precision details.

Critical Values:

A clinically significant value of an analyte that requires immediate medical intervention.

-Previously referred to as “Panic Levels”
-Often requires repeat for confirmation
-MUST be immediately telephoned to the physician and documented.
-Communicable diseases: must notify department of health

Systems of Measurement:

The UNIT defines the dimensions (volume, mass,
concentration, time) of a measured analyte (test).

Three systems in use:
 Metric System
 Conventional Units: the amount of dissolved mass
 International System (SI System): the number of dissolved molecules (measured in moles)

International System of Units (SI System)

Accepted internationally in 1960
Based upon Metric System (but NOT the same!)
Consists of 7 basic units
Meter
Kilogram
Second
Mole
Ampere
Kelvin
Candela
And....... derived units

Derived units:

obtained by combining basic units
through multiplication/division

SI Units:

Basic and Derived units can be too large or too small
-NOT used in Canada for many tests
Prefixes are used to express multiples of submultiples of the units

Significant Figures (decimal precision):

The minimum number of digits needed to express
a particular value in scientific notation without
loss of accuracy.

Biological Variation:

the natural variability in a lab test due to
physiologic differences among subjects and within the same subject over time

Sig figs lab:

1. Patient results should be expressed to the same decimal precision as used to express the Reference Interval for a test
2. Good quality control practice reports control results to one additional significant figure when possible.

Example:
Glucose: Normal Range: 4.0 – 6.0 mmol/L
PATIENT: reported to 1 decimal point (ex. 4.1 mmol/L)
CONTROL: reported to 2 decimal points (ex. 4.11 mmol/L)

Rounding Off:

1. If the number to be removed is less than 5 round down
Ex: 6.423 becomes 6.42

2. If the number to be removed is greater than or equal to 5 round up
Ex: 6.427 becomes 6.43
6.425 becomes 6.43

Post-Analytical Processes:

-Call critical values
- Report results
-Interpret results
-Verify results
-Phone/send results to health care provider
-Store Specimens (prepare samples accordingly)
-Specimen retention
-Retention of results

Information Systems:

HIS (Hospital Information System): Computerized system linking all areas/processes of patient care in the hospital

-Assigns unique identification number for patient upon admission
-Captures Patient Demographics
-Facilitates Order Entry (by physicians, nurses, etc)
-Captures other patient info
-Medications, diagnoses, diagnostic tests
-Keeps electronic record of all activities associated with a patient admission

The Laboratory Information System (LIS):

-Integration w/HIS allows transfer of information (w/o
manual transcription)

-Facilitates capture of demographics, order entry,
date/time of collection/testing, specimen
requirements, physician information, test specifics,
quality control results, and just about anything you
can think of!!!!

-Analyzer Interface: communication software
linking analyzer output directly to LIS

Advantages of the LIS:

-Documentation of sample handling, analysis,
reporting
-Captures date/time/operator for each step
-Provides a means to relay interpretative
messages and reference interval information to
the health care provider
-Documents handling of critical values
-Tracks volumes/workload/patient billing
-Provides a database for investigations and quality
assurance measures

MLTS:

-Venipuncture
-Run Lab tests
-Develop and evaluate the tests
-Interpret data
-Assess results
-Communicate with physicians regarding test results
-Perform, assess quality control/QA/QM
-Equipment maintenance/troubleshooting
-Inventory

Millimoles(mmol/L) to micromoles (umol/L)?

x 1000

Why is the reporting unit used extremely important in the clinical laboratory?

to interpret result with the reference intervals

Single test order:

GLU

Multiple selected test orders:

GLU, UREA, CREA

Profile (Panel) orders:

LYTES, LIPIDS
A set of tests ordered together using one profile name

Standing Orders (aka Recurring Orders):

A set of tests (automatically) repeated at a designated interval

Add-Ons:

after blood collected, add on additional tests (usually requires a phone call to the lab)