Type of test Blood

Normal findings

 Total WBCs

 Adult/child > 2 years: 5000-10,000/mm3 or 5-10 × 109/L (SI units)

Child ≤ 2 years: 6200-17,000/mm3

Newborn: 9000-30,000/mm3

Possible critical values

WBC count < 2500 or > 30,000/mm3

Test explanation and related physiology

The WBC count has two components. The first is a count of the total number of WBCs (leukocytes) in 1 mm3 of peripheral venous blood. The other component, the differential count, measures the percentage of each type of leukocyte present in the same specimen. An increase in the percentage of one type of leukocyte means a decrease in the percentage of another. Neutrophils and lymphocytes make up 75% to 90% of the total leukocytes. The total leukocyte count has a wide range of normal values, but many diseases may induce abnormal values.

An increased total WBC count (leukocytosis: WBC count > 10,000/mm3) usually indicates infection, inflammation, tissue necrosis, or leukemic neoplasia. Trauma or stress, either emotional or physical, may increase the WBC count. A decreased total WBC count (leukopenia: WBC count < 4000/mm3) occurs in many forms of bone marrow failure (e.g., after antineoplastic chemotherapy or radiation therapy, marrow infiltrative diseases, overwhelming infections, dietary deficiencies, and autoimmune diseases).

The major function of the WBCs is to fight infection and react against foreign bodies or tissues. Five types of WBCs may easily be identified on a routine blood smear (see blood smear, p. 151). These cells, in order of frequency, include neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

WBCs are divided into granulocytes and nongranulocytes. Granulocytes include neutrophils, basophils, and eosinophils. Neutrophils have multilobed nuclei and are sometimes referred to as polymorphonuclear leukocytes (PMNs or polys). The nor mal ranges for absolute counts depend on age, sex, and ethnicity. For example, the normal range for absolute neutrophils for African American men is 1400 to 7000 cells/microliter.

Neutrophils, the most common granulocyte, are produced in 7 to 14 days, and exist in the circulation for only 6 hours. The primary function of the neutrophil is phagocytosis (killing and digestion of bacterial microorganisms). Acute bacterial infections and trauma stimulate neutrophil production, resulting in an increased WBC count. Often when neutrophil production is significantly stimulated, early immature forms of neutrophils enter the circulation. These immature forms are called band or stab cells. This occurrence, referred to as a shift to the left in WBC production, is indicative of an ongoing acute bacterial infection.

Basophils (also called mast cells), especially eosinophils, are involved in the allergic reaction. Parasitic infestations also are capable of stimulating the production of these cells. These cells are capable of phagocytosis of antigen–antibody complexes. As the allergic response diminishes, the eosinophil count decreases. Eosinophils and basophils do not respond to bacterial or viral infections.

Nongranulocytes (mononuclear cells) include lymphocytes, monocytes, and histiocytes. Lymphocytes are divided into two types: T-cells and B-cells. Whereas T-cells are primarily involved with cellular-type immune reactions, B-cells participate in humoral immunity (antibody production). The primary function of the lymphocytes is fighting chronic bacterial and acute viral infections. The differential count does not separate the T- and B-cells but rather counts the combination of the two.

Monocytes are phagocytic cells capable of fighting bacteria in a way very similar to that of neutrophils. However, monocytes can be produced more rapidly and can spend a longer time in the circulation than neutrophils.

The WBC count and differential counts are routinely measured as part of the complete blood count (p. 270). Serial WBC counts and differential counts have both diagnostic and prognostic value. For example, a persistent increase in the WBC count (particularly the neutrophils) may indicate a worsening of an infectious process (e.g., appendicitis). A dramatic decrease in the WBC count below the normal range may indicate marrow failure. In patients receiving chemotherapy, a reduced WBC count may delay further chemotherapy.

The absolute count is calculated by multiplying the differential count (%) by the total WBC count. For example, the absolute neutrophil count (ANC) is helpful in determining the patient’s real risk for infection. It is calculated by multiplying the WBC count by the percent of neutrophils and percent of bands; that is,

If the ANC is less than 1000, the patient may need to be placed in protective isolation because he or she could be severely immunocompromised and at great risk for infection.

 Interfering factors

 • Physical activity and stress may cause an increase in WBC and differential values.

 • Pregnancy and labor may cause increased WBC levels.

 • Patients who have had a splenectomy have a persistent, mild elevation of WBC counts.

* Drugs that may cause increased WBC levels include adrenaline, allopurinol, aspirin, chloroform, epinephrine, heparin, quinine, steroids, and triamterene.

* Drugs that may cause decreased WBC levels include antibiotics, anticonvulsants, antihistamines, antimetabolites, antithyroid drugs, arsenicals, barbiturates, chemotherapeutic agents, diuretics, and sulfonamides.

 Procedure and patient care

 • See inside front cover for Routine Blood Testing.

• Fasting: no

• Blood tube commonly used: lavender

Abnormal findings

 Increased WBC count (leukocytosis)

- Infection

- Leukemic neoplasia

- Trauma

- Stress

- Tissue necrosis

- Inflammation

Decreased WBC count (leukopenia)

- Drug toxicity

- Bone marrow failure

- Overwhelming infections

- Dietary deficiency

- Autoimmune disease

- Bone marrow infiltration (e.g., myelofibrosis)

- Congenital marrow aplasia

Increased/decreased differential count

 See Table 1.

Table1. Causes of abnormalities in white blood cell (WBC) and differential counts

Table1. Causes of abnormalities in white blood cell (WBC) and differential counts—cont'd

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم العلاقات العامة يسلم دعوة الملتقى التربوي التنسيقي الثاني لتربية محافظة ذي قار

شعبة فاطمة بنت أسد تجري الاختبارات النهائية للمشاركات في دورة هدى للناس

قسم الشؤون الفكرية يصدر الجزأين الأول والثاني من سلسلة تاريخ الاستعمار

جمعت بين الدقة والجمال.. متحف الكفيل يضم سجادة نادرة تعود لأكثر من ثمانية عقود

المزيد

الآخبار الصحية

عناصر منزلية قد تؤثر على الخصوبة وفرص الحمل

شكل الدماغ قد يتنبأ بخطر الخرف قبل سنوات

طريقة صينية بسيطة للوقاية من السكري

هل تساعد المانغو في الوقاية من السكري؟

المزيد

الآخبار التكنلوجية

رقم غامض ولا إنترنت.. متوجون بنوبل للطب لم يعلموا بفوزهم

"سيري" تحت المجهر.. تحقيق فرنسي جديد ضد شركة "آبل"

أميركيان وياباني يفوزون بجائزة نوبل للطب

تحول غير مسبوق.. إنستغرام تمنح مفاتيحها للمستخدمين

المزيد

مواضيع ذات صلة

white blood cell scan (WBC scan, Inflammatory scan)

vitamin D (25-hydroxy vitamin D2 and D3 ; 1,25-dihydroxyvitamin D [1,25(OH)2 D])

Basal Hormone Measurements of Testis

vitamin B12 (Cyanocobalamin and methylmalonic acid [MMA])

virus testing

viral cultures

Laboratory Investigations of Pheochromocytoma and Paraganglioma

varicella virus testing (Antibody testing for Varicella zoster virus, Varicella zoster virus [VZV], Herpes virus-3)

uroporphyrinogen-1-synthase

urine culture and sensitivity (C&S)

uric acid, blood, and urine

urea breath test (UBT, Helicobacter pylori breath test)