Reference ranges in clinical analysis

1. REFERENCE RANGE I
Samuel Wiafe Mintah

2. OBJECTIVES
▪ UNDERSTAND THE CONCEPT OF
REFERENCE RANGE
▪ FACTORS TO CINSIDER IN SETTING
REFERENCE RANGE

3. A

4. B

5. C

6. D

7. CONCEPT OF REFERENCE RANGE
Patient test results produced from
laboratories are used by clinicians to
make medical diagnosis, screen, assess
physiologic functions, enable treatment,
monitor and manage therapy.

8. CONCEPT OF REFERENCE RANGE CONT'D
▪Clinical laboratory reference ranges
are vital events for clinical diagnosis,
prognosis, treatment, and monitoring
of any health complications. So
locally established reference range is
required to correctly interpret clinical
laboratory results

9. ▪ During interpretation of laboratory data,
measured test values are compared to
reference ranges, considered to be the
range in which “normal” values fall
(Solberg, 2006; Rohan et al., 2007;
McCudden et al., 2010)

10. ▪By reference range we intend to know
what is normal and what is not.
▪ The first function of a clinician is to decide if
the patient belongs to a group of individuals
defined as “healthy” or to the group of
individuals who do not belong to the group
defined as “healthy”

11. ▪ It is, therefore, important to identify the state
of health or disease.
▪ As Schneider (1960) states, “healthy persons
are defined as those who have values of
specific and selected attributes not
characteristic of those defined states which
seem important for the immediate purposes of
the physician making the classification”

12. ▪ What is health?
▪The World Health Organization
(WHO) defines health as “a state of
complete physical, mental and social
well-being and not merely the absence
of disease or infirmity” (WHO, 1948)

13. ▪ The International Federation of Clinical
Chemistry defines ‘‘reference range’’ as the
value obtained by observation or measurement
of a particular type of quantity on a reference
individual where the individual is selected
using defined criteria.

14. ▪ Reference values are typically reported as
Reference Ranges (RRs) comprising 95%
of a healthy reference population; which
are widely used in the process of
providing medical diagnosis, therapeutic
management, or other pathologic and
physiological evaluations

15. ▪ For the interpretation of clinical chemistry
parameters, a reference range of a clinical
chemistry parameter has a set of values
▪ The establishment of a reference range that is
specific for the reference population is vital
and international guidelines also recommended
a reference range for all clinical laboratory
tests.

16. ▪Any healthy individual is different in
different countries, in a different
period in the same country, in
different age groups and sex.
▪The definition of health is a relative
and not an absolute state.

17. ▪Unless appropriate data for
comparison is provided a
patient’s laboratory result simply
is not medically useful.

18. ▪ For appropriate diagnosis, treatment, and follow-
up of patients, the correct interpretation of the
laboratory results is mandatory.
▪ This is attained by knowing the normal reference
intervals that have been established in the local
setting considering climate, socioeconomic status,
living style, and genetic makeup than using values
from other areas of the world.

19. ▪ In most African countries, however, reference
intervals have not been adequately addressed.
▪ Clinical laboratory reference ranges are vital
events for clinical diagnosis, prognosis, treatment,
and monitoring of any health complications. So
locally established reference range is required to
correctly interpret clinical laboratory results

20. DEFINITIONS
▪Reference Individual: This a
person selected for testing on the
basis of well-defined criteria. They
are usually assumed to be
"healthy".

21. DEFINITIONS
▪Reference Population: This is
a group of persons who meet
the defined criteria for a
reference individual.

22. DEFINITIONS
▪Reference Interval: The interval
between, and including, two
reference limits, which are values
derived from the distribution of
results obtained from a sample of
a reference population” (Ceriotti,
et al., 2008)

23. DEFINITIONS
▪Reference Sample: An adequate
number of reference individuals
meeting the selection criteria to
be included into the sampling
group and who represent the
reference population.

24. DEFINITIONS
▪Reference value: This is the
value, test result obtained by
measurement or observation of
a specific quality or quantity of
any reference individual.

25. DEFINITIONS
▪Reference limits: The value of
the upper limits and the lower
limits of the reference
distribution, and are estimates
of true limits.

26. DEFINITIONS
▪Inclusion or Exclusion
criteria: Determining factor
to determine eligibility of a
person to be included or
excluded from the population
selected for reference study.

27. USE OF PUBLISHED REFERENCE INTERVALS
▪ Interpreting clinical data using
inappropriate RI may lead to
misclassification of a patient, which can
result in misdiagnoses, improper treatments
or both Unless a RI is representative of the
patient's demographics and is determined
using similar preanalytical procedures and
comparable analytical methods, it is not
appropriate as a diagnostic reference for
clinical decision-making

28. ▪ Reference intervals published in textbooks, journal
articles, and web-based databases or provided by
instrument manufacturers may or may not contain
sufficient information to determine whether the RI is
appropriate for a particular patient The quality of a
RI depends on the reference sample size, the use of
procedures to detect and eliminate outliers, and
correct use of statistical procedures to estimate the
reference limits

29. CAUTION
▪Published RI should be used with
caution, and only when sufficient
information is available to
determine their quality and
applicability to the patient and
analytical method

30. ▪THANK YOU