Immunology and Allergy – Exam Review Set 1

Immunology and Allergy — free preview

Question 1 of 2

Reference values

Typical paediatric values. A real laboratory quotes its own ranges, and several of these move with age.

Vital signs by age

Age	Heart rate	Respiratory rate	Systolic BP — hypotension below
Term newborn	110–160	30–40	60 mmHg
1–12 months	110–160	30–40	70 mmHg
1–2 years	100–150	25–35	70 + (2 × age) mmHg
2–5 years	95–140	25–30	70 + (2 × age) mmHg
5–12 years	80–120	20–25	70 + (2 × age) mmHg
Over 12 years	60–100	15–20	90 mmHg

Other bedside measures

Measure	Reference	Note
Temperature	36.5–37.5 °C	38.0 or above is fever
Oxygen saturation	94–100 percent in air	under 92 in air needs oxygen and admission
Capillary refill	under 2 seconds	3 seconds or more suggests shock
Heart rate	see the table above	age dependent
Respiratory rate	see the table above	age dependent
Blood pressure	see the table above for the hypotension floor	hypertension: systolic over roughly 105 mmHg at 1–2 y, 112 at 2–5 y, 118 at 5–12 y, 130 over 12 y
Ejection fraction	55–70 percent	under 40 percent is systolic failure
Valve gradient (echo)	mean gradient under 25 mmHg is mild; 25–40 moderate; above 40 severe	for aortic stenosis – the peak instantaneous gradient reads higher than the mean, so check which one is quoted
Troponin	below the assay cut-off in a well child	a rise means myocardial injury, most often myocarditis in this age group

Arterial blood gas

Measure	Reference	Note
pH	7.35–7.45
PaCO₂	35–45 mmHg (4.7–6.0 kPa)	the respiratory term
PaO₂	80–100 mmHg (10.6–13.3 kPa)	breathing room air
Bicarbonate	22–26 mmol/L	the metabolic term
Base excess	−2 to +2 mmol/L
Lactate	under 2 mmol/L	over 4 marks shock
A–a gradient	under 10–15 mmHg in air	a normal gradient means the lungs are not the problem

Lung function and body fluids

Measure	Reference	Note
FEV₁ / FVC	FEV₁ 80 percent or more of predicted; ratio above 0.85 in children	asthma severity is graded on FEV₁ off treatment: 80+ mild, 60–80 moderate, under 60 severe
Bronchodilator reversibility	a rise of 12 percent or more in FEV₁	this is what makes obstruction reversible, and it is the asthma test
Pleural fluid – exudate	protein above 30 g/L (3 g/dL), or fluid to serum protein above 0.5; LDH ratio above 0.6	pH 7.2 or below, glucose under 2.2 mmol/L, or frank pus means it needs a drain
Dehydration	5 percent mild, 10 percent moderate, 15 percent severe	estimated clinically – each 1 percent is 10 mL/kg of deficit

Haematology

Measure	Reference	Age note
Haemoglobin	see age note	newborn 14–22 g/dL; physiological nadir 9.5–13.5 at 6–9 weeks; 6 months to 6 years 10.5–14; 6–12 years 11.5–15.5
White cells	see age note	newborn 9–30 ×10⁹/L; 1 year 6–18; 4–10 years 4–13.5; adolescent 4.5–11
Neutrophils	neutropenia under 1.5 ×10⁹/L, severe under 0.5
Lymphocytes	see age note	the lymphocyte and neutrophil lines CROSS twice: lymphocytes predominate from about 1 week to 4 years, neutrophils either side of that
Eosinophils	under 0.5 ×10⁹/L, or under 5 percent
Platelets	150–450 ×10⁹/L
MCV	lower limit roughly 70 + age in years (fL)	to about 12 years
ESR	under 10–20 mm/h
CRP	under 5–10 mg/L	laboratory dependent

Anaemia and coagulation tests

Measure	Reference	Note
Ferritin	15–150 µg/L (ng/mL)	a low value proves iron deficiency, but it is an acute phase protein, so a normal one during infection or inflammation does not exclude it
Serum iron / transferrin saturation	saturation under 16 percent suggests iron deficiency	iron is low in both iron deficiency and anaemia of chronic disease; the iron binding capacity is high in the first and low in the second
Reticulocyte count	0.5–1.5 percent	high means the marrow is responding, as in haemolysis or blood loss; low with anaemia means the marrow is the problem
Haematocrit	newborn 45–65, child 33–43 percent	above 65 percent in a newborn is polycythaemia
Prothrombin time / APTT	PT 11–14 s, APTT 25–38 s	an isolated long APTT with normal platelets suggests haemophilia; both prolonged suggests vitamin K deficiency, liver disease or consumption
Factor VIII / IX activity	50–150 percent of normal	severe disease is under 1 percent, moderate 1–5, mild 5–40
Fibrinogen	1.5–4.0 g/L	falls in consumption; it is also an acute phase protein, so a normal value during sepsis may already represent a fall
D-dimer	raised in consumption and in thrombosis	infection and inflammation raise it too, so a high value is not specific
Haemoglobin electrophoresis	HbA2 under 3.5 percent, HbF under 2 percent beyond infancy	HbA2 above 3.5 percent identifies beta thalassaemia trait; it is falsely lowered by coexisting iron deficiency
Haptoglobin / LDH	haptoglobin falls and LDH rises in haemolysis; LDH roughly under 300 U/L in a well child	read them beside the reticulocyte count and the bilirubin. LDH is also a bulk-of-disease marker in leukaemia and lymphoma and rises in tumour lysis
Direct antiglobulin test	negative in a healthy child	a positive test means antibody is bound to the red cells, which separates immune haemolysis from every other kind

Electrolytes and renal

Measure	Reference	Note
Sodium	135–145 mmol/L
Potassium	3.5–5.0 mmol/L	up to 6.0 in the newborn
Chloride	98–107 mmol/L
Bicarbonate	22–26 mmol/L	same value as on the gas
Urea	2.5–6.5 mmol/L (7–18 mg/dL)
Creatinine	infant 15–35, child 25–60, adolescent 50–90 µmol/L	rises with muscle mass, so an adult range over-reads a child
Glucose	3.5–5.5 mmol/L (63–99 mg/dL)	newborn above 2.6 mmol/L
Urine sodium / chloride	under 20 mmol/L means the loss is not renal	a high urine chloride points to the kidney or a diuretic

Liver, bone and metabolic

Measure	Reference	Note
ALT / AST	10–40 / 10–45 U/L
GGT	5–35 U/L	up to 200 in the first months of life
Alkaline phosphatase	child 100–400 U/L, higher in the growth spurt	an adult range makes normal childhood bone turnover look like disease
Bilirubin (total)	under 17 µmol/L (1 mg/dL) beyond the newborn period
Conjugated bilirubin	under 17 µmol/L, or under 20 percent of total	above this is always pathological
Albumin	35–50 g/L
Cholesterol / triglycerides	total cholesterol under 4.4 mmol/L, triglycerides under 1.5 mmol/L	both rise steeply in nephrotic syndrome, in proportion to the albumin loss
Total protein	60–80 g/L	albumin plus globulin – a low total with a low albumin points to loss rather than to synthesis
INR / prothrombin time	INR 0.8–1.2	the earliest measure of failing liver synthesis, and it does not correct with vitamin K once the liver is the problem
Creatine kinase	under 200 U/L	thousands mean muscle: a Duchenne CK runs 10 000 to 20 000 from infancy
Ammonia	newborn under 110, child under 50 µmol/L
Calcium / magnesium / phosphate	2.2–2.7 / 0.7–1.0 / 1.2–2.0 mmol/L	phosphate runs higher in infancy, to about 2.6
Lipase or amylase	three times the upper limit defines pancreatitis
Sweat chloride	under 30 normal, 30–59 intermediate, 60 or more diagnostic
Caeruloplasmin	0.2–0.6 g/L	low in Wilson disease, and it is an acute phase protein, so a normal level during inflammation does not exclude it
Parathyroid hormone	1.6–7.5 pmol/L	rises early in chronic kidney disease, before calcium or phosphate move
Antistreptolysin O titre	under 200 IU/mL in most children	peaks 3–6 weeks after a streptococcal throat infection; a single raised value shows exposure, not active disease
Malaria parasitaemia	any level is abnormal	above 2 percent counts as severe in a non-immune child, and above 10 percent is an indication for exchange transfusion in some protocols

Endocrine and hormones

Measure	Reference	Note
Thyroid stimulating hormone	0.5–5.0 mIU/L beyond the newborn period	it surges to 20 or more in the first days of life, so a newborn screen is read against its own threshold and not against this range
Free T4	12–22 pmol/L	a low free T4 with a high TSH is primary hypothyroidism; a low free T4 with a low or normal TSH points to the pituitary
Cortisol	morning 140–500 nmol/L	the value only means something beside the time and the clinical state: under 100 during hypoglycaemia or shock is inappropriately low
ACTH	2–11 pmol/L (10–50 ng/L)	high with a low cortisol is adrenal failure; high with a high cortisol points above the adrenal
17-hydroxyprogesterone	under 10 nmol/L after the first few days	grossly raised in 21-hydroxylase deficiency, and the newborn screening analyte for congenital adrenal hyperplasia
Growth hormone / IGF-1	a random growth hormone is uninterpretable; peak over 7 µg/L on provocation is normal	IGF-1 is read against age and pubertal stage, and is low in malnutrition as well as in deficiency
LH / FSH	prepubertal under 0.3 IU/L	an LH above 0.3 with a pubertal response to stimulation means the axis has switched on, which is what separates central from peripheral puberty
Testosterone / oestradiol	prepubertal testosterone under 0.5 nmol/L, oestradiol under 20 pmol/L
HbA1c	under 42 mmol/mol (6.0 percent)	48 mmol/mol (6.5 percent) or more is diagnostic of diabetes; it is unreliable when red cell survival is shortened
Insulin / C-peptide	should be undetectable when glucose is low	any measurable insulin during a hypoglycaemic episode is abnormal and is the whole diagnosis in hyperinsulinism
Ketones (blood)	under 0.6 mmol/L	3.0 or more with acidosis defines ketoacidosis; absent ketones during hypoglycaemia is the abnormal finding, not a reassuring one
25-hydroxyvitamin D	sufficient above 50, deficient below 25 nmol/L	this is the storage form and the one to measure; the active 1,25 form can be normal or high in nutritional rickets
Plasma metanephrines	any clear elevation is abnormal	the screening test for a catecholamine-secreting tumour; caffeine and several drugs raise it falsely
Renin / aldosterone	both read against sodium intake and posture	renin rises in salt-losing states and is suppressed when mineralocorticoid excess is driving the blood pressure

Metabolic screening

Measure	Reference	Note
Anion gap	8–16 mmol/L	sodium minus chloride and bicarbonate. Above 16 means an unmeasured acid: lactate, ketones, an organic acid or a toxin
Uric acid	0.12–0.35 mmol/L (2–6 mg/dL) in children	high in tumour lysis, renal failure and several inborn errors; low in molybdenum cofactor deficiency
Plasma phenylalanine	under 120 µmol/L	the newborn screening analyte; treatment is started above about 360 µmol/L and the level guides dietary control
Plasma amino acids / urine organic acids	qualitative	the PATTERN names the disorder rather than any single value, and the sample must be taken during the acute illness to be interpretable

Tumour markers

Marker	Reference	Note
Alpha-fetoprotein	adult and child under 10 ng/mL (under 8 kU/L)	very high at birth and falls to the adult range by about 8 months, so a neonatal value must be read against age; raised in hepatoblastoma, yolk sac tumour and germ cell tumours
Urinary catecholamines	homovanillic and vanillylmandelic acid, reported against urinary creatinine	raised in about nine in ten neuroblastomas, which is why the urine test comes before any biopsy

Immunology and coeliac serology

Measure	Reference	Note
Total IgA	see age note	1–3 years 0.2–1.0, 4–6 years 0.3–1.3, school age 0.5–2.0, adult 0.8–3.0 g/L. Selective IgA deficiency is under 0.07 g/L
IgG / IgM	IgG 5–16 g/L, IgM 0.5–2.0 g/L beyond infancy	IgG falls to a physiological trough at 3–6 months as maternal antibody clears
Tissue transglutaminase IgA	negative under 7 U/mL; 10x the upper limit supports coeliac disease	it is an IgA antibody, so it reads falsely negative when total IgA is low – always check the total IgA beside it
C3 / C4	C3 0.75–1.65 g/L, C4 0.14–0.54 g/L	a low C3 that recovers by 8–12 weeks is post-infectious nephritis; one that stays low beyond that points to C3 glomerulopathy or membranoproliferative disease, and a low C4 alongside it suggests lupus

Cerebrospinal fluid

Measure	Newborn	Child
White cells	0–20 /mm³	0–5 /mm³
Protein	0.4–1.2 g/L	0.15–0.45 g/L
Glucose	at least 60 percent of the blood glucose	at least 60 percent of the blood glucose
Bacterial pattern	hundreds to thousands of neutrophils, high protein, low glucose	same

Score: 0 / 0

Pediatric Case ReviewPediatric Exam Review Sets

This content is for members. First, create a free account to browse samples — then choose a plan to unlock everything. Already a member? Log in here.

What this deck covers

Immunology and Allergy – Exam Review Set 1 in 50 board-style clinical cases with worked explanations. Each case gives you a clinical vignette, four options, the correct answer, and an explanation of why each of the other three is wrong, with the guideline or textbook it follows named on the answer.

Board-style teaching questions for paediatricians and trainees preparing for paediatric board, MRCPCH and licensing examinations. Written from published guidelines and standard paediatric textbooks, with the source named on every answer.

The 50 cases, in order

A boy with no tonsils
Infections and low platelets
No IgA at all
Low IgG in a thriving baby
What the infusions are for
Thrush that would not clear
A test on the heel prick card
Diarrhoea that would not stop
Eczema, bruising and infections
Unsteady with red eyes
Abscesses in the liver
A cord that took five weeks
Ulcers and swollen gums
Ulcers every three weeks
Tablets every day
Meningococcus for the second time
Swelling that ignores treatment
Heart, palate and infections
Lupus that runs in the family
Slipping away over months
Which child to investigate
Where to start the tests
Matching bug to defect
Ordering blood for this baby
Normal immunology, still infected
Egg in a cake but not scrambled
Negative results, obvious symptoms
Vomiting two hours after rice
A test result in a well child
When can he have it again
Itchy mouth from raw fruit
Labelled allergic at two
Can he have a cephalosporin
Wheeze after a painkiller
Flushing during an infusion
Weals every day for months
Weals in a hot bath
A dip in a chilly lake
Weals that bruise
Swollen lips overnight
Better already, wanting to leave
Starting at a new school
Proving it afterwards
Carrying it but not using it
How to use the pen
Blocked nose all year
Food sticking in the chest
Blood in a happy baby’s nappy
Preventing the next allergy
Hay fever that beat the sprays

Diagnoses and management options tested

Across the fifty cases you are asked to choose between options such as: Common variable immunodeficiency, X-linked agammaglobulinaemia, T cell receptor excision circles, A stem cell transplant, Cyclical neutropenia, Antibody deficiency, An inherited early complement component deficiency, Because the genetic panel cannot detect it, Repeating the immunology tests in six months, IgE-mediated rice allergy, Systemic anaphylaxis to multiple fruits, IgE-mediated allergy to ibuprofen specifically, Exercise-induced anaphylaxis, Total immunoglobulin E.

Clinical pearls from this deck

Look at the tonsils. No lymphoid tissue anywhere in a boy with recurrent infection is a diagnosis you can make with a torch.
Autoimmunity in a child with recurrent infection is not a coincidence. In this condition the two are the same disease.
This diagnosis is usually made by a coeliac test that failed. Understanding why explains both the finding and what to do next.
A number that is low can still be a system that works. Test the function, not just the level, before labelling a child.
The outcome that matters is the lungs. Every chest infection prevented is bronchiectasis that does not happen.
Read the lymphocyte count against the infant range, not the adult one. A number that looks unremarkable on an adult form is catastrophic at four months.

Work through the deck once for recognition, then again a week later to test yourself — each question gives the answer and explains why every other option fails.

More from this system: all immunology and allergy case decks · pediatric reference values.

Immunology and Allergy – Exam Review Set 1

Vital signs by age

Other bedside measures

Arterial blood gas

Lung function and body fluids

Haematology

Anaemia and coagulation tests

Electrolytes and renal

Liver, bone and metabolic

Endocrine and hormones

Metabolic screening

Tumour markers

Immunology and coeliac serology

Cerebrospinal fluid

Case Complete

The rest of this set is for members

What this deck covers

The 50 cases, in order

Diagnoses and management options tested

Clinical pearls from this deck

Leave a Comment Cancel Reply

Vital signs by age

Other bedside measures

Arterial blood gas

Lung function and body fluids

Haematology

Anaemia and coagulation tests

Electrolytes and renal

Liver, bone and metabolic

Endocrine and hormones

Metabolic screening

Tumour markers

Immunology and coeliac serology

Cerebrospinal fluid

Case Complete

The rest of this set is for members

What this deck covers

The 50 cases, in order

Diagnoses and management options tested

Clinical pearls from this deck

Related Posts

Leave a Comment Cancel Reply