Author: All Pediatrics

Blog: What is Normal Part two

What is Normal?

Part two: Lab work

In medicine, people often put great faith in testing and instruments. For example, studies have shown that for asthma, using an inhaler with a spacer is as effective as using a nebulizer. The former has the advantages of being easier to use, portability, and requiring less time. Nevertheless, many people, including many doctors, believe the latter is better, not because of any data, but simply because it uses a machine. So what about lab testing? This can give objective findings, and one assumes it will easy to determine normal from abnormal.
However, this is not always so. As with growth curves, abnormal is defined as a certain percentage of the population, regardless of health status. Furthermore, if you run large numbers of tests on a healthy person, the odds increase that at least one of them will fall outside the ‘normal’ range. What we are often looking for is the degree of abnormality. Suppose I am concerned that your child may have a liver disorder, and his liver enzyme test comes back at 32, with 30 being the upper limit of normal. Is that a concern? Almost certainly not, whereas a finding of 150 would be.

Blood testing for food allergies is another common area where testing is not as definitive as you might expect. If a random allergy panel is ordered, many children will have abnormal results, yet the child can tolerate those foods without difficulty. Without clinical correlation of symptoms, the tests are often worthless, and do not warrant avoiding those foods.

A similar area, undergoing further revision at present, is with vitamin D levels. Until recently, levels below 30 were felt to need treatment, but newer studies have called this into question. Thus, if there is any concern about vitamin D, it makes more sense to make sure your child is taking in enough, usually by milk (which has vitamin D added to it), or a vitamin supplement (non-milk dairy products are good sources of calcium, but usually do not have added vitamin D), rather than measuring a level.

When I first started doing pediatrics, we used to do many tests routinely, such as a yearly urine. We no longer do this, because it has been shown to be of little value. Thus, we would often find protein in the urine, a marker for a condition called nephrotic syndrome. However, protein can be found normally in children if they have been up and about during the day. If we found protein in the urine on a random sample, we would have the parents collect a urine first thing in the morning. This would invariably be negative, and then we would not worry about it. I have seen many patients with nephrotic syndrome over the years, but never one found by a ‘routine’ urine specimen; they always had clinical findings which directed me to look for it.

Compounding the situation further, no test is perfect, and results can be misleading. This comes up particularly when we consider Bayes’ theorem. You can find the mathematics behind this on-line, but basically, if your child has almost zero probability of having a given disease, a positive test changes that to just being very improbable. Results are similar if a child is very likely to have a condition, but the test is negative. Testing is most valuable when the physician is uncertain.

We can look at Lyme disease as a specific example. If your child comes to the office in the summer with the classic rash (Erythema Chronicum Marginatum), I will treat for Lyme disease, regardless of what a test showed, so there is no need to test. Conversely, testing for Lyme disease in someone with vague, non-Lyme complaints is not a good idea; a positive test would be a false positive, not indicative of Lyme disease. I remember one patient in particular, who I felt was depressed. The parents did not agree with the diagnosis, and went to see a self-proclaimed ‘chronic Lyme expert.’ The child’s Lyme test was negative, but he tested positive for a tick disease seen only on the west coast, a place he had never visited. The child wound up leaving the practice to be treated with long-term antibiotics by the ‘expert’ for a disease he almost certainly did not have; I doubt it helped.

Even when a test is correct, it may still not mean anything. For example, some children are strep carriers. They always have strep in their throat, living with it just fine, not contagious, and not needing treatment. However, if I were to randomly culture them, I would find strep. We don’t do such random cultures, of course. Now suppose that same child came to the office with a runny nose, cough, no fever, no vomiting, no enlarged lymph glands, and a scratchy throat. They do not have a ‘strep throat’ either, but if I were to culture them, ‘just to be sure,’ the test would be positive. This would then mean the child needed to be quarantined for a bit, and take ten days of antibiotics (which will usually not eradicate the strep in a carrier), all for nothing.

Is there a role for any routine testing nowadays in pediatrics? Yes. Many infants are anemic, so we test their blood at 9 months. We are seeing more cholesterol problems, and so we recommend testing for this somewhere between the 9–11-year visit. Lastly, I harken back to elevated BMI (see part one of this series). With the increase we are seeing in type 2 diabetes, even in children, current thinking is to look for this. The test is a hemoglobin A1C, and I order it in older children who are above the 95th percentile in BMI, or the 85th percentile with other factors (e.g., a positive family history).

Next up: medical disorders

What is Normal? Blog from Dr. Farber

What is normal?

Part one:

In pediatrics, we often talk about a child, or a finding, being normal, but the term can be vague for many parents.  What exactly do we mean when we say your child is normal?

Sometimes, we use it to refer to something that is common.  Thus, it is normal for a two-year-old to have tantrums, or for a preschooler to have multiple viral infections in the winter.  Another meaning of the word, and the one I will discuss today, is in a numerical or statistical sense.

Here, we are not talking about an absolute number, but a range.  Thus, although many people think of a normal temperature as 98.6, in actuality it can range between 97 and 100.3 degrees, and we do not consider it a fever until it hits 100.4.

Statistically, the 50th percentile is average.  This means when we take a measurement, half of children will be at or above this value, and half at or below.  Importantly, this leads to the finding that being below average is, in most instances, normal.  I will use height as an example; an adult male who is 5 foot 8 is shorter than average, but no one would consider that abnormal. The 90th percentile in height means your child is taller than 90 out of 100 children their age, and the 10th percentile means they are taller than 10 out of 100 (or, alternatively, shorter than 90).  Arbitrarily, someone above or below the 5th percentile can be considered abnormal.

One conclusion to draw from this is that, by definition 10 percent of children are ‘abnormal’ on any given measure (5% above, and 5% below).  Intuitively, this does not sound correct, and in most cases, it is indeed not.  A professional basketball player who is 6 foot 6 is ‘abnormal,’ but if you try and find a cause with blood tests and the like, you will almost certainly not find anything, unless there is something else going on (for example, Marfan syndrome leads to extreme height and can have cardiac issues, so that playing basketball is not healthy for such a person, but there are other clues on the exam beside the height, which will direct us to look further).  Similarly, most children who are shorter than normal do not have genetic or other conditions, and a work-up would be unproductive

Growth curves are used as a guide, to tip us off to when something may be amiss.  Someone who is well below the fifth percentile in height, or has other associated features, is worth evaluating further.  The rate of growth is usually even more important; a child who has always been at the third percentile, and continues to grow along those lines, is usually not a concern. However, the child who used to be at the 75th percentile, and then 25th, and is now at the 5th is, even though he is taller than the child at the third percentile.  In this case, the growth rate, not the absolute height, is abnormal, and warrants investigation.  This is also why regular physical examinations are important, to help detect trends, and not just measurements at one point in time.

One very important point to make is that, for young children, normal predicts normal, nothing else.  Thus, a child who is a slow walker, but normal, will not necessarily be below average in athletic skills when older.  In the same manner, a taller than average child may wind up short (but normal) as an adult.  Better predictions, but still rather inaccurate, would be based on genetic information (tall parents usually produce tall adults.)

Another important aspect of growth is weight.  This is a valuable marker in the younger child/infant, but again we are usually most interested in the trend over time, rather than the absolute number (for example, has your newborn baby regained the birthweight by the two-week visit, and are they gaining around an ounce a day?).  Even more important than the weight is the Body Mass Index (BMI), which takes into account height as well.  Thus, going back to our tall basketball player, he might weigh 200 pounds, but that would not make him overweight, unlike a person the same weight but a foot shorter.  In older children, BMI is the key number I like to look at, in helping to decide how a child is doing here.

Unfortunately, as you are all aware, this country has been getting heavier, and this applies to children as well.  We are seeing an epidemic of diabetes in this country, and it is spreading to children.  We are often able to diagnose prediabetes, a precursor to diabetes, in children.  We can prevent diabetes in many, if not most cases, by establishing a good weight; thus, we recommend screening by blood work for older overweight children.

BMI is also an exception to the rule that above the 95th percentile is the cutoff for abnormal.  This is because of the rising incidence of excessive weight in this country.  Suppose you are at the 50th percentile for BMI, and suddenly everybody in the country gained 50 pounds overnight; you would still be at the 50th percentile when compared to everyone else, but nobody would argue that your current weight was healthy.  For BMI, therefore, we tend to use the 85th percentile for helping to decide who should be screened for diabetes (if you are at or above this, and have a family history of diabetes, I screen, and also if you are at or above the 95th percentile, regardless).

Next up:  abnormal lab tests

March Schedule Now Open

Our March schedule is now open.

You can book your well check appointments right from our website at

Update on available appointments

Since early October, we have seen a dramatic increase in the number of children with acute and severe respiratory illnesses. We have also seen a significant increase in the number of Mental Health visits. As we head into the holidays, we anticipate the continued spread of respiratory viruses. Because of this, as well as ongoing staffing issues, we have temporarily limited the number of well check appointments scheduled during the winter months.

If you have a child that is due for a well visit, (older than 2 years of age), we ask that you place your child on our waitlist; we will use the waitlist aggressively when respiratory illnesses decrease.

You may add your child to the waitlist by sending a portal message. Please add the office you prefer to be seen at as well as any provider preference.

We appreciate your patience as we use the resources we have to care for your children during this historic time.

February schedule now open

Our February schedule is now open. You can book directly from our website at

If you have a child that is due for a well visit,  (older than 2 years of age), but are not able to find an appointment, we ask that you place your child on our waitlist; we will use the waitlist aggressively when respiratory illnesses decrease.
You may add your child to the waitlist by sending a portal message. Please add the office you prefer to be seen at as well as any provider preference.

Holiday Hours

During the holiday season, our hours will change so that our physicians and staff can spend extra with their families. We will always be available by phone; you may reach our on call nurse service by calling 703 436 1200 and following the prompts. We wish you all a happy and safe holiday season!

Flu and RSV info

Our Triage Nurses are overwhelmed by volume! If you have a question that is not urgent, we will return your call when we have time. **Please note that all of the local urgent cares and emergency rooms are also overwhelmed by volume.**
For general questions about Flu and RSV, please reference the website. Please see these specific links for Flu and RSV.

Flu: What Parents need to know

RSV: When it is more than just a cold

Update from Dr. Caplan

Good Morning,

I wanted to take a moment to address the frustration you must feel regarding appointment availability and the paucity of vaccine clinics. Believe me, we share in your frustration. There has been a confluence of events that have led us here.

– Demand for well visits is up considerably (many people delayed routine care during the pandemic).
– Staffing (not unlike the rest of the nation) the offices has been very difficult.
– Mental health visits have increased significantly.
– Unusually busy respiratory virus season

These are not excuses but a recognition of the reality of our practice.
I would like to take this opportunity to advocate strongly for influenza and COVID vaccinations for your child. As mentioned above, already the respiratory viral burden is unprecedented. I am aware of the difficulty of obtaining these vaccines in our clinic, however, other community resources are available and do a very good job (please see links in the comments for resources).

We are very proud of our call center staff, triage nurses, floor nurses and providers. They are working tirelessly to care for our ALL Pediatrics community of families.

Michael S. Caplan MD
Managing Partner
All Pediatrics