Malabsorption is characterized by the inability to digest or absorb nutrients from the small intestine into the bloodstream and is related to diseases of the pancreas, liver, and intestine. Test choice depends on the clinician’s suspicion regarding the etiology of the malabsorption (eg, carbohydrate malabsorption versus fat malabsorption). “Shotgun” approaches to malabsorption evaluations are not recommended.
Quick Answers for Clinicians
ARUP Laboratory Tests
Assess for fecal blood
Qualitative Immunoassay
Do not use to diagnose inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS); may be used for monitoring IBD activity
Qualitative Enzyme-Linked Immunosorbent Assay
Aid in differentiation of IBD from IBS and other functional disorders of the gastrointestinal (GI) system
Aid in monitoring of IBD and prediction of relapse
Not specific for IBD
Not diagnostic for IBD
Does not distinguish celiac disease (CD) from ulcerative colitis
Results may fluctuate as disease activity fluctuates
False negatives are more common in children than adults
Quantitative Chemiluminescent Immunoassay
Aid in the diagnosis of GI infections caused by common protozoal pathogens
Do not order for patients with diarrhea developed during prolonged hospitalization
Use as a sensitive alternative to traditional, insensitive ova and parasite examinations of stool specimens for the evaluation of GI infections
Detect Cryptosporidium hominis, C. parvum, Cyclospora cayetanensis, Dientamoeba fragilis, Entamoeba histolytica, and Giardia lamblia/intestinalis/duodenalis
Due to periodic shedding of some parasites, a result of “not detected” cannot completely rule out infection with these parasites
If clinical signs and symptoms persist, an additional specimen for testing may be indicated
Viral and bacterial gastroenteritis are more common than parasite gastroenteritis and should be considered as alternative diagnoses
Asymptomatic infections are known to occur and, therefore, correlation of test results with clinical signs and symptoms is imperative
Panel does not detect helminths (flatworms, roundworms, and flukes), nonpathogenic protozoa, Cystoisospora, or microsporidia
Negative result does not rule out presence of polymerase chain reaction (PCR) inhibitors in specimen or assay-specific nucleic acid in concentrations below the level of detection
Qualitative Polymerase Chain Reaction
Aid in the diagnosis of GI infections caused by pathogenic bacteria
Use as a sensitive alternative to traditional stool culture to detect the most common GI bacterial pathogens, including Salmonella, Shigella/enteroinvasive E. coli, Campylobacter jejuni/coli, and Shiga-toxigenic E. coli
Can also detect Campylobacter upsaliensis, which cannot be readily cultured
Negative result does not rule out presence of PCR inhibitors in the patient specimen, test-specific nucleic acid in concentrations below the level of detection
Molecular assays will not detect rare or unusual enteric bacterial pathogens that are not specifically targeted by the test (eg, Aeromonas, Plesiomonas, Yersinia, Vibrio, and enterotoxigenic E. coli)
A bacterial isolate is not obtained if antimicrobial susceptibility testing is indicated
Qualitative Polymerase Chain Reaction
Evaluate carbohydrate malabsorption due to disaccharidase deficiency
Quantitative Spectrophotometry
Carbohydrate malabsorption assessment (indirect)
Presence of reducing substance suggests carbohydrate malabsorption
Most useful in children who are unable to undergo lactose tolerance or hydrogen breath tests
Qualitative Colorimetry
Carbohydrate malabsorption assessment (indirect)
Acidic pH (<5.5) suggests carbohydrate (lactose) malabsorption
Quantitative pH Indicator Strips
Preferred reflex screening test for CD
May aid in monitoring adherence to gluten-free diet (GFD)
Correlation between CD serologic tests may be variable at low antibody titers, early disease, or treatment with GFD; strong clinical correlation is recommended
At screening dilution, endomysial antibody (EMA) may show prozone phenomenon; if suspicion for disease is strong, consider testing for tissue transglutaminase (tTg) and/or deamidated gliadin peptide (DGP) antibodies
Sera containing antismooth muscle antibodies (ASMA) will interfere with the detection of EMA IgG; sera should be further tested at higher dilutions
False-negative results possible in early disease, in individuals on GFD, and with use of immunosuppression
With false-positive results, consider early disease and/or specific risk for CD
Small bowel biopsy and/or HLA DQ typing may be important in establishing a diagnosis of CD based on patient’s age, clinical symptoms, and/or risk for disease
Quantitative Immunoturbidimetry/Semi-Quantitative Enzyme-Linked Immunosorbent Assay//Semi-Quantitative Indirect Fluorescent Antibody
Measurement of fecal fats can be useful in establishing a diagnosis of pancreatic disease
Use for random stool collection
Qualitative Microscopy/Stain
Measurement of fecal fats can be useful in establishing a diagnosis of pancreatic disease
Testing requires submission of an aliquot from a 24-, 48-, or 72-hour stool collection
For random stool collection, refer to qualitative fecal fat test
For complete 24-hour stool collections, order 24-hour quantitative fecal fat test
For complete 48-hour stool collections, order 48-hour quantitative fecal fat test
For complete 72-hour stool collections, order 72-hour quantitative fecal fat test
Nuclear Magnetic Resonance Spectroscopy
Measurement of fecal fats can be useful in establishing a diagnosis of pancreatic disease
Testing requires submission of an entire 24-hour stool collection
For random stool collection, refer to qualitative fecal fat test
For testing of an aliquot from a 24-, 48-, or 72-hour stool collection, order the quantitative fecal fat test
For complete 48-hour stool collections, order 48-hour quantitative fecal fat test
For complete 72-hour stool collections, order 72-hour quantitative fecal fat test
Nuclear Magnetic Resonance Spectroscopy
Measurement of fecal fats can be useful in establishing a diagnosis of pancreatic disease
Testing requires submission of an entire 48-hour stool collection
For random stool collection, refer to qualitative fecal fat test
For testing of an aliquot from a 24-, 48-, or 72-hour stool collection, order the quantitative fecal fat test
For complete 24-hour stool collections, order 24-hour quantitative fecal fat test
For complete 72-hour stool collections, order 72-hour quantitative fecal fat test
Nuclear Magnetic Resonance Spectroscopy
Measurement of fecal fats can be useful in establishing a diagnosis of pancreatic disease
Testing requires submission of an entire 72-hour stool collection
For random stool collection, refer to qualitative fecal fat test
For testing of an aliquot from a 24-, 48-, or 72-hour stool collection, order the quantitative fecal fat test
For complete 24-hour stool collections, order 24-hour quantitative fecal fat test
For complete 48-hour stool collections, order 48-hour quantitative fecal fat test
Nuclear Magnetic Resonance Spectroscopy
Screen for exocrine pancreatic function
Quantitative Chemiluminescent Immunoassay
Assess for presence of anemia and leukocytosis
Automated Cell Count
Assess for inflammatory processes
Quantitative Ion-Selective Electrode/Enzymatic
Panel includes anion gap, carbon dioxide, chloride, potassium, and sodium
Preferred test to detect acute phase inflammation (eg, autoimmune diseases, connective tissue disease, rheumatoid arthritis, infection, or sepsis)
Quantitative Immunoturbidimetry
Nonspecific test used to detect inflammation associated with infections, cancers, and autoimmune diseases
Visual Identification
Initial screening test for hepatobiliary inflammation
Quantitative Enzymatic/Quantitative Spectrophotometry
Panel includes albumin; alkaline phosphatase (ALP); aspartate aminotransferase (AST); alanine aminotransferase (ALT); bilirubin, direct; protein, total; and bilirubin, total
Screen for other causes of malabsorption
Quantitative Enzymatic
Quantitative Enzymatic
May assist in assessing nutritional status or indicating a possible chronic process
Quantitative Spectrophotometry
Assess thyroid function
Identify risk in patients with palpable thyroid nodules
Quantitative Electrochemiluminescent Immunoassay
Reflex pattern: if thyroid stimulating hormone (TSH) is outside the reference interval, then free T4 testing will be added
Preferred test for screening and monitoring of thyroid function
Quantitative Chemiluminescent Immunoassay
Determine whether to use IgA or IgG tissue transglutaminase (tTG) and deamidated gliadin peptide (DGP) assays
Quantitative Immunoturbidimetry
Recommended single screening test for IgA-deficient individuals with suspected celiac disease (CD)
IgA testing recommended to identify IgA deficiency prior to choosing tTG test
May aid in monitoring adherence to gluten-free diet (GFD) in CD-confirmed patients
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Recommended rapid, stand-alone diagnostic test for Clostridium difficile-associated diarrhea
Qualitative Polymerase Chain Reaction
Quantitative Freezing Point
Quantitative Ion-Selective Electrode
Assess fat malabsorption
Quantitative Spectrophotometry
Use for nutritional assessment of vitamin A (retinol and retinyl palmitate) in serum or plasma
Quantitative High Performance Liquid Chromatography
Preferred test to diagnose vitamin D insufficiency and monitor response to therapy
Testing is recommended only for patients at risk for vitamin D insufficiency
Quantitative Chemiluminescent Immunoassay
Use for nutritional assessment of vitamin E (alpha- and gamma-tocopherols)
Quantitative High Performance Liquid Chromatography
Aid in detection of vitamin B12 deficiency in individuals with macrocytic or unexplained anemia, or unexplained neurologic disease
Quantitative Chemiluminescent Immunoassay
Carbohydrate (lactose) malabsorption assessment
Not recommended: replaced by hydrogen breath test
Quantitative Enzymatic
Pancreatic exocrine function assessment
Not recommended; elastase measures are better
Quantitative Enzymatic/Spectrophotometry
Medical Experts
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References
18431067
20889735
25716699
Chapman TP, Chen LY, Leaver L. Investigating young adults with chronic diarrhoea in primary care. BMJ. 2015;350:h573.
Choosing Wisely
Choosing Wisely. An initiative of the ABIM Foundation. [Accessed: Dec 2020]
15949151
17468550
22085666
18431059
19699409
18192963
Schiller LR. Management of diarrhea in clinical practice: strategies for primary care physicians. Rev Gastroenterol Disord. 2007;7 Suppl 3:S27-S38.
Reflex pattern: test begins with immunoglobulin A; depending on findings, one or more of the following tests may be added for clinical interpretation
Tissue Transglutaminase Antibody, IgA
Tissue Transglutaminase Antibody, IgG
Endomysial Antibody, IgA by IFA
Deamidated Gliadin Peptide (DGP) Antibody, IgA
Deamidated Gliadin Peptide (DGP) Antibody, IgG
Celiac Disease Dual Antigen Screen