levels occurring from 1800 to 2300 hours. Hormones Secreted by the Pituitary Gland Anterior pituitary Posterior pituitary Intermediate lobe Growth hormone Oxytocin MSH

 

Studies have demonstrated that in patients with known

CAD on treatment with statins (lipid lowering drugs),

levels of apo B and apo A-I were a significant predictor for

Diagnostic Immunology 729

recurrent cardiovascular events as compared to plasma

LDL–C and TC (Total cholesterol) levels.

Quantia Apo B is a turbidimetric immunoassay for the

quantitative determination of apolipoprotein B in human

serum.

AUTOMATION IN TURBIDIMETRY

Quantimate Turbidimetry Analyzer (Fig. 23.17)

Optimized Measuring System

¾ Preprogramed for Quantia reagents

¾ Adaptable turbidimetric immunoassay reagents

¾ Backup analyzer for routine chemistries

¾ End point, kinetic, fixed time, multistandard (MSD)

and absorbance modes

¾ 90 open locations including 40 open locations for MSD

¾ Six programing modes in MSD

¾ Automatic flagging of outlying results

¾ Plug and play system.

Instrument Specifications

• Measuring system : Cuvette mode

• Filter range : 340, 405, 505, 546, 578, 630

• Temperature : 37oC

• Measuring range : –200 to +2.0 OD

• Photometric accuracy : 2% from 0 to 2.0 OD

• Photometric linearity : +1%

• Reading volume : Minimum 1.0 mL in

macrocuvettes,

 Minimum 0.3 mL in

semimicrocuvettes

• Keyboard : 10 digital keys and

8 functional keys

• Display : Back illuminated LCD with

32 characters

• Thermal printer : 20 columns

FIG. 23.17: Quantimate turbidimetry analyzer

Troubleshooting

Immunoturbidimetry Tests

For Product Range

Quantia-RF, Quantia-ASO, Quantia-CRP, Quantia-CRP US, Quantia-MA, Quantia-IgG, Quantia-IgM, Quantia-IgA,

Quantia-C3, Quantia-C4, Quantia-AT III, Quantia-Lp(a), Quantia-Fibrinogen, Quantia-Apo-A1, Quantia-Apo-B

Problem: Testing errors

Possible causes Solutions

Pipettes and Pipetting

1. Use of wet, contaminated or damaged pipettes Before testing, check whether the pipettes are wet, contaminated or damaged to avoid

errors in testing

2. Improperly calibrated micropipettes Prior to testing, check if the micropipettes are being used for a long-time without being

recalibrated

3. Inadequate pipette volumes Ensure that small volumes of reagent or sample are not pipetted out with large volume

pipettes

4. Contamination of reagent or sample pipetted Use fresh tips during pipetting of reagent as well as sample to avoid contamination of

the same

Contd...

730 Concise Book of Medical Laboratory Technology: Methods and Interpretations Temperature and Time

1. Inadequate reagent temperature Prior to commencing of the testing procedure, ensure that the reagents and samples

are at the assay temperature so recommended

Equipments

1. Contaminated cuvettes Check whether the cuvettes are free from foreign matter. Also, ensure that the solution

in the cuvettes is free of other foreign matter and air bubbles

 Cleanlines of cuvettes will help in eliminating contamination

2. Incorrect wavelength Ensure that correct wavelength is used in testing

3.  Hardened or clogged filters Filters need to be checked periodically to avoid hardening and loss in efficacy over a

period of time

Storage and Procedure

1. Inadequate storage conditions Ensure proper storage of kits before and after use

for longer life of the reagents

2. Error in performing the test Ensure that the procedure and addition sequence is followed as indicated in the

package insert

Problem: Errors in real sample blanking and immediate mixed blanking methods

Possible causes Solutions

Low absorbance values

1. Change in the time interval for measuring Ensure correct time interval for measuring absorbances A1 and A2 to

absorbance A1 and A2 can lead to early or avoid erroneous results

delayed mesurement than the actual

reaction time

2.  Improper incubation temperature Temperature influences the rate of formation of immune complexes; therefore, it

should be optimized to obtain accurate results

3. High or low absorbance of calibrator Ensure that the sample is added properly while performing the test

during calibration

4. Increase in concentration of calibrator Avoid evaporation of the calibrator in order to obtain desired concentration.

5. Deterioration of reagent Partial deterioration of the reagent can give low reactivity and hence low absorbance

values

 Ensure that proper storage conditions are adhered to

6. Incorrect sample used If plasma is used instead of serum, low absorbance values may be obtained. Follow

proper procedural steps for use of sample

7. Sample has analyte concentration beyond Dilute the sample and rerun the test

the prozone limit

8. Differences in reactivity between antigen If the latex based reagents are not mixed well before use, variations

and antibody are observed leading to in readings are observed. Therefore, it is of utmost importance

variations in readings obtained to mix the latex based reagents well before pipetting to avoid variation in readings.

Besides, dispensing and mixing well it is also important to mix the reagent well with

the sample to trigger optimum reaction between antigen and antibody to obtain correct

absorbance values

High absorbance values

1. Deterioration of calibrator Deterioration of the calibrator can give high absorbance values. Ensure that proper

storage conditions are adhered to

Contd...

24

The Endocrine System

C H A P T E R

INTRODUCTION

The science concerned with the structure and functions of

the endocrine glands and the diagnosis and treatment of

disorders of the endocrine system is called endocrinology.

This term comes from the Greek words ‘endo’ (within),

‘crine’ (to secrete) and ‘logos’ (study of).

The endocrine system consists of glands situated in

different areas of the body as shown in Figure 24.1. Each

gland produces different hormones, which regulate the

activity of other organs and tissues in the body. These

hormones are released directly into the blood flowing

through the gland. This is in contrast to exocrine glands,

which release hormones down a tube or duct.

Glands are functional units of hormone-secreting cells

located in various regions of the body making up the

endocrine system. Each gland has specific functions that

help to maintain the normal internal environment and

promote the survival of the organism. Although, there are

some diffuse endocrine tissues, as in the gastrointestinal

epithelium, there are several major glands or control

centers within the endocrine system.

PITUITARY GLAND

The pituitary gland, which lies in a small depression in

the sphenoid bone of the skull called the sella turcica, has

often been termed the ‘Master Gland’ because many of the

hormones, it releases affect the release of other hormones.

However, the pituitary is really not the master. It is

controlled by a brain region called the hypothalamus via

the release of releasing factors into a special blood vessel

FIG. 24.1: Endocrine glands

732 Concise Book of Medical Laboratory Technology: Methods and Interpretations

network (hypothalamic-hypophyseal portal system) that

feeds the pituicytes. These releasing factors then cause or

inhibit the release of pituitary hormones, which travel via

the circulatory system to the target organ (Fig. 24.2).

Anatomically and functionally the pituitary can be

divided into three portions.

Anterior Pituitary (Adenohypophysis)

Six peptide hormones are secreted by the adenohypo-physis:

¾ Growth hormone (somatotropin, GH)

¾ Corticotropin (ACTH)

¾ Thyroid-stimulating hormone (TSH)

¾ Follicle-stimulating hormone (FSH)

¾ Luteinizing hormone (LH)

¾ Prolactin (PRL).

All hormones except growth hormone and prolactin

regulate the activities of other glands. Somatotropin, PRL

and ACTH are polypeptide hormones and LH, FSH, and

TSH are glycoproteins having very similar structures.

The ACTH is an anterior pituitary hormone that

stimulates cortisol and androgen production by the

adrenal gland. Diurnal variation of ACTH are typical, with

peak levels occurring from 0600 to 0800 hours and trough

levels occurring from 1800 to 2300 hours.

Hormones Secreted by the Pituitary Gland

Anterior pituitary Posterior pituitary Intermediate lobe

Growth hormone Oxytocin MSH

TSH ADH

FSH

LH

ACTH

Prolactin

The regulation of hormones elaborated by the

endocrine glands is complex and varied. The tropic

hormones of the anterior pituitary are regulated by CNS

factors (hypothalamic-releasing hormones) as well as by

products of their target organs. A delicate balance is thus

maintained. Antidiuretic hormone (ADH) is regulated

by osmotic pressure and volume. Parathormone is

controlled by calcium and phosphorus concentrations,

norepinephrine and epinephrine by direct neural stimuli;