Sputum from a 58-year-old man with pneumonia is sent for Gram stain and culture. It is thin and watery, and under low power shows 30 squamous epithelial cells and 5 pus cells per field. The best action is to:

Reject it and request a deep-cough sample

Concentrate it and do an AFB smear

Report it as negative for pathogens

Culture it and report all organisms

Clinical pathology: feces and sputum

14 Kerala PSC Lab Technician Gr II practice questions on Clinical pathology: feces and sputum, part of Pathology. The first 14 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
By NTEP grading of a Ziehl-Neelsen sputum smear, 25 acid-fast bacilli seen in 100 oil-immersion fields are reported as:
1. A1+
2. B2+
3. CScanty
4. D3+
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Answer: A · 1+
NTEP (India) grading follows the WHO/IUATLD scale: 1-9 AFB in 100 fields is 'scanty' (the exact number is recorded), 10-99 AFB in 100 fields is 1+, 1-10 AFB per field (at least 50 fields read) is 2+, and more than 10 AFB per field (at least 20 fields read) is 3+. Twenty-five bacilli in 100 fields therefore falls in the 1+ band. A smear is called negative only after 100 fields show no AFB. The grade helps follow the response to treatment.
- B: 2+ needs an average of 1-10 bacilli in every field.
- C: Scanty is used for only 1-9 bacilli in 100 fields.
- D: 3+ needs more than 10 bacilli per field.
Question 2 · Easy
A 58-year-old man has iron deficiency anemia but no visible blood loss. Which stool test is most useful?
1. AStool pH
2. BFecal occult blood test
3. CReducing sugar test
4. DSudan fat stain
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Answer: B · Fecal occult blood test
Slow bleeding from the gut, for example from hookworm infestation, peptic ulcer or colorectal cancer, can cause iron deficiency without visible blood in the stool. Chemical tests such as orthotoluidine, benzidine or guaiac use the peroxidase-like activity of hemoglobin to turn a colourless chromogen blue or green. Red meat and peroxidase-rich vegetables can give false positives, so they are avoided for 3 days before a chemical test. Immunochemical tests for human hemoglobin avoid this diet problem.
- A: Stool pH helps in sugar intolerance and does not detect bleeding.
- C: Reducing sugars in stool point to carbohydrate (lactose) intolerance, not bleeding.
- D: A Sudan stain shows fat malabsorption, not blood loss.
Question 3 · Easy
Charcot-Leyden crystals in sputum or stool are formed from the breakdown of:
1. ANeutrophils
2. BRed cells
3. CEosinophils
4. DEpithelial cells
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Answer: C · Eosinophils
Charcot-Leyden crystals are colourless, slender, double-pointed crystals made of a protein (galectin-10) from eosinophils. In sputum they suggest bronchial asthma or allergic lung disease, often with Curschmann's spirals. In stool they point to parasitic infection, such as amoebic dysentery or helminths. Seeing them in a stool smear is a reason to search harder for parasites.
- A: Neutrophil breakdown gives pus, not Charcot-Leyden crystals.
- B: Red cell breakdown gives hemosiderin or hematoidin, not these crystals.
- D: Epithelial cells do not form Charcot-Leyden crystals.
Question 4 · Hard
A 2-year-old has had frothy, watery diarrhea after milk feeds for a week. Stool: pH 5.0, reducing substances positive, no pus cells, no ova or cysts, Sudan stain negative. What is the most likely cause?
1. ALactase deficiency
2. BAmoebic colitis
3. CPancreatic insufficiency
4. DShigella dysentery
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Answer: A · Lactase deficiency
Undigested lactose reaches the colon, where bacteria ferment it to acids and gas; this gives frothy, watery stools with a pH below 5.5 and reducing sugar in the stool. The absence of pus cells argues against an invasive infection, and a negative Sudan stain rules out fat malabsorption. Lactase deficiency often follows an intestinal infection in young children (secondary lactose intolerance). The stool must be tested fresh, because bacteria keep fermenting the sugar on standing.
- B: Amoebic colitis gives blood and mucus, with trophozoites on a wet mount.
- C: Pancreatic insufficiency causes fatty stools with a positive Sudan stain.
- D: Shigella dysentery gives blood, mucus and many pus cells in the stool.
Question 5 · Hard
Sputum from a 58-year-old man with pneumonia is sent for Gram stain and culture. It is thin and watery, and under low power shows 30 squamous epithelial cells and 5 pus cells per field. The best action is to:
1. AConcentrate it and do an AFB smear
2. BReport it as negative for pathogens
3. CCulture it and report all organisms
4. DReject it and request a deep-cough sample
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Answer: D · Reject it and request a deep-cough sample
Squamous epithelial cells come from the mouth, so more than 10 per low-power field shows heavy saliva contamination, and few pus cells show the sample is not from the lower airway. Culturing it would grow mouth flora and could mislead treatment. A good sample has fewer than 10 squamous cells and more than 25 pus cells per low-power field. The patient should rinse the mouth and cough deeply, ideally in the early morning.
- A: An AFB smear was not asked for and does not fix a saliva sample.
- B: A negative report would be false, because the sample does not represent the lungs.
- C: Culture would grow mouth flora that cannot be told apart from true pathogens.
Question 6 · Medium
Stool from a 5-year-old with bloody diarrhea and fever shows sheets of pus cells, many red cells and large macrophages, but no trophozoites. This picture most suggests:
1. ACholera
2. BBacillary dysentery
3. CAmoebic dysentery
4. DGiardiasis
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Question 7 · Easy
Chemical tests for occult blood in stool, such as the guaiac test, depend on the:
1. ABinding of antibody to human globin
2. BIron released from hemoglobin
3. CConversion of heme to bilirubin
4. DPeroxidase-like activity of heme
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Question 8 · Medium
Why is an early-morning sputum sample preferred for AFB microscopy?
1. ASaliva later in the day kills the bacilli
2. BBacilli multiply fastest during the night
3. CMorning sputum needs no concentration step
4. DOvernight secretions pool and contain more bacilli
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Question 9 · Easy
In the Ziehl-Neelsen method for sputum AFB under the national TB programme, the decolourizer is:
1. A3% acid alcohol
2. B95% ethyl alcohol
3. C25% sulphuric acid
4. D1% acetic acid
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Question 10 · Hard
A 35-year-old man has had cramping abdominal pain and stools with blood-stained mucus for 10 days, with little fever. Saline mount of fresh stool: few pus cells, clumped red cells, Charcot-Leyden crystals and motile cells with finger-like pseudopodia containing ingested red cells. What is the most likely diagnosis?
1. ABacillary dysentery
2. BBalantidiasis
3. CGiardiasis
4. DAmoebic dysentery
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Question 11 · Medium
A 12-year-old with recurrent wheeze coughs up thick sputum. Wet mount shows coiled mucus threads, many eosinophils and colourless, pointed hexagonal crystals. Most likely diagnosis:
1. ALung abscess
2. BPulmonary tuberculosis
3. CBronchial asthma
4. DLobar pneumonia
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Question 12 · Medium
A 30-year-old in a flood relief camp passes profuse, painless, watery stools with flecks of mucus and a fishy smell. Microscopy shows very few pus cells and no red cells. Most likely cause:
1. ACholera
2. BAmoebic dysentery
3. CShigellosis
4. DUlcerative colitis
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Question 13 · Medium
A large daily dose of which substance can make a guaiac test for fecal occult blood falsely negative?
1. ARaw turnip
2. BAspirin
3. CVitamin C
4. DRed meat
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Question 14 · Easy
Which stain is used on a stool smear to show excess fat in suspected malabsorption?
1. ASudan III
2. BLeishman
3. CZiehl-Neelsen
4. DLugol's iodine
Answer and explanation in LearnFree account

Clinical pathology: feces and sputum

By NTEP grading of a Ziehl-Neelsen sputum smear, 25 acid-fast bacilli seen in 100 oil-immersion fields are reported as:

A 58-year-old man has iron deficiency anemia but no visible blood loss. Which stool test is most useful?

Charcot-Leyden crystals in sputum or stool are formed from the breakdown of:

A 2-year-old has had frothy, watery diarrhea after milk feeds for a week. Stool: pH 5.0, reducing substances positive, no pus cells, no ova or cysts, Sudan stain negative. What is the most likely cause?

Sputum from a 58-year-old man with pneumonia is sent for Gram stain and culture. It is thin and watery, and under low power shows 30 squamous epithelial cells and 5 pus cells per field. The best action is to:

Stool from a 5-year-old with bloody diarrhea and fever shows sheets of pus cells, many red cells and large macrophages, but no trophozoites. This picture most suggests:

Chemical tests for occult blood in stool, such as the guaiac test, depend on the:

Why is an early-morning sputum sample preferred for AFB microscopy?

In the Ziehl-Neelsen method for sputum AFB under the national TB programme, the decolourizer is:

A 12-year-old with recurrent wheeze coughs up thick sputum. Wet mount shows coiled mucus threads, many eosinophils and colourless, pointed hexagonal crystals. Most likely diagnosis:

A 30-year-old in a flood relief camp passes profuse, painless, watery stools with flecks of mucus and a fishy smell. Microscopy shows very few pus cells and no red cells. Most likely cause:

A large daily dose of which substance can make a guaiac test for fecal occult blood falsely negative?

Which stain is used on a stool smear to show excess fat in suspected malabsorption?