Lab Tests During Childhood Illness

Common tests:

CBC (Complete Blood Count)

Here the lab sends blood through a counter and determines the quantity of RBCs, WBCs and platelets per cu. mm. This can usually be done from a finger prick. Chinese like this test for ill children and interpret whether the illness is bacterial or viral, based on the elevation of the WBC. They believe that a "High white count" (say 15,000 to 20,000) signifies a bacterial process and necessitates antibiotics.

Differential. Here the lab examines and counts the white cells under the microscope and determines the percentage of each type of cell. When leukocytes predominate over lymphocytes, especially immature leukocytes called "Bands," it's thought to indicate bacterial infection. This count may also be done by the mechanical counter, which is less precise, but results in percentages down to the decimal, eg, 62.3% neutrophils. Most machines do not separate mature leukocytes from bands, and may add other types, like eosinophils, basophils and monocytes to various categories.

Analysis: This test is not too helpful in making a precise diagnosis, because studies show many viruses go through phases that include high white counts, elevated bands, etc. It's an excellent test for determining anemia and red cell diseases like sickle cell and thalassemia, or for leukemia.

If the doctor intends to give antibiotics regardless of the result, it's probably best to question the need for these tests, but many times in China, it's unavoidable.

ESR and CRP (Erythrocyte Sedimentation Rate and C-Reactive Protein):

These tests react similarly and go up when the body is experiencing inflammation. This is useful when one is considering diseases like rheumatoid arthritis and auto-immune diseases like regional enteritis or ulcerative colitis. As therapy works, one repeats the test. to monitor when to reduce therapy.

Analysis: Not usually indicated, helpful in special situations

Electrolytes

Blood is examined for potassium, sodium, bicarbonate and chloride. Irregularities in their concentrations, often caused by dehydration, must be treated promptly.

Urinalysis

Here a clean, fresh urine specimen is dipsticked to change indicator paper colors and reveal Specific gravity, (a measure of dehydration) pH, RBCs, WBCs, nitrites (which indicate bacterial acting on the urine) ketones (a measure of starvation) and several other measures.

Urine culture: a sterilly collected urine sample (which may require catheterization) is incubated for 3 days to grow any bacteria infecting the urine. The lab, when it finds a bacteria, sub-cultures it to determine which antibiotics can kill it.

Analysis: Highly useful tests in many conditions. It can show dehydration, nephritis (blood in the urine), urinary tract infection, as well as other less common problems. In general, a urinalysis is sufficient to decide whether to start antibiotics. A culture should be done prior to antibiotics to clarify what organism is infecting the person. If the lab reports several bacteria, it probably means the urine was not properly collected and contamination occurred. A count of "Greater than 100,000 colonies per milliliter" of a particular bacteria is the level used to diagnose a bacterial urine infection.

Strep culture

When sore throat could be caused by the strep bacteria, a culture swabbed from the back of the throat may be done, or a rapid strep test, which is almost as good, may show the presence of the strep bacteria. Penicillin should be used for + results.

Mononucleosis test

Blood is sent looking for the EB virus, the cause of Mono. Since Mono may resemble Strep, or the much more worrisome Kawasaki disease, sometimes both Strep and Mono tests are done. Occasionally the Mono test is negative, but turns positive if repeated a few days later.

Analysis: I decide to treat strep on a clinical basis, but need the test to advise others in the family should they become sick in the next few days. Strep is associated with rheumatic fever, so treating it early and universally is the correct approach.

Lead level

This is usually a screening blood test to discover who may have encountered excessive lead. Lead is devastating to children's brains and any amount should be avoided. Every child should get the test around a year of age and occasionally thereafter, to assure that this silent peril is avoided.

Chest Xray

This is exposure of the child to a very small dose of x-rays to see the contents of the chest. Heart, mediastinum, lung fields, bones, diaphragms, shoulders, clavicles and trachea are seen in detail. It's useful one time to see the size of the heart when there is a pathologic murmur, or when asthma or pneumonia symptoms are not simple. I don't advise it if the physical exam and diagnosis are obvious and it would not change my therapy anyway.

Analysis: Many doctors use this test because it's there and they don't trust their physical exam. It does have very low risk and is not a dangerous test, unlike a CT (Computerized tomography)

ECG

A painless electronic tracing of the heart used to assess arrythmias and sizes of the chambers of the heart, when heart disease is suspected. Takes about a minute to run and computers give a good analysis of the result, although in pediatrics, an expert should review the tracing.

Echocardiogram

When heart disease is present, the extent of the problem can be detailed via passing sonic waves over the heart and vessels to determine the precise problem and how soon therapy is needed.

Abdominal Ultrasound

Essentially harmless Sound waves are passed over the abdomen to assess kidneys, ureters, liver, spleen, bladder, gall bladder, female organs and some of the intestines. It's  very useful for suspected appendicitis, ovarian problems, kidney problems, gall bladder problems, etc.

Bone Xrays

Taken of injured bones to see how best to treat them. The amount of xray is increased beyond the chest xray amount in order to penetrate the dense bones.

Hip ultrasound

Some countries screen for dislocated hips with this test, which, although benign, is costly and not necessary if an experienced pediatrician examines the baby's hips.

Newborn tests

"PKU:" a heel stick sample is sent to assess for congenital inherited diseases associated with retardation. The key ones are for thyroid and galactosemia, which are not rare, and for adrenogenital syndrome, which can be lethal.

Bilirubin: We turnover 1% of our red cells each day. They are processed in the liver. Newborn's liver can be overwhelmed by this process, especially if they had delivery complications. They get yellow from the toxic pigment, bilirubin, and hospitals check its elevation, to avoid deposition of excess levels into the brain tissue. It is also checked if liver disease at any age is suspected, along with "Liver enzyme" levels, which are quite low normally, but rise dramatically if liver cells are being destroyed, like with hepatitis.

Hearing test. All newborns now get a screen to see if they react to sounds in each ear, so hearing-impaired children can be recognized and treated early.

About Dr. Richard Thomas MD, FAAP. Dr. Thomas is an American Board Certified Pediatrician. He and his wife, Dr. May Khadem, an ophthalmologist, recently arrived to Shanghai from Chicago, Illinois to join the team of doctors at WorldPath Clinic International and American Sino. Dr Thomas' last position was a Chair of Ambulatory Pediatrics at Cook Country Hospital in Chicago, Illinois, and faculty at Rush Medical College where he was for seven years. Prior to that he was in private practice. Dr. Thomas has a special interest in early childhood literacy promotion, asthma, eczema, and allergic rhinitis.