The question
Work it with the BNF open before you show the answer. At exam pace this item has 1 min 12 s.
An 82-year-old woman is seen at her residential home by the duty general practitioner because staff report 3 days of increasing confusion and daytime drowsiness; she is normally orientated and washes and dresses herself. She has no burning on passing urine, no urinary frequency or urgency, no new incontinence and no suprapubic or loin pain, and the home's observation charts record no fever. She has opened her bowels once in 5 days. A urine specimen sent 2 days ago as part of the home's routine has been reported.
PMH: osteoporosis with a vertebral fracture 3 weeks ago; hypertension; chronic kidney disease.
DH: codeine phosphate 30 mg PO 6-hrly (back pain, started 3 weeks ago), amlodipine 5 mg PO daily (hypertension), alendronic acid 70 mg PO weekly with colecalciferol (osteoporosis). No known drug allergies.
SH: lives in a residential home; does not smoke; drinks no alcohol.
On examination: Temperature 36.7°C, HR 78/min and rhythm regular, BP 128/74 mmHg, RR 16/min, O₂ sat 96% breathing air. Drowsy but rousable, orientated to person only, inattentive; 4AT score 5. No new focal neurological signs. Chest clear. Abdomen soft with palpable faecal loading in the left iliac fossa; no suprapubic tenderness and no renal angle tenderness; bladder not palpable. No catheter. Weight 58 kg.
Investigations: Hb 124 g/L (115–165), WCC 7.8 ×10⁹/L (4.0–11.0), neutrophils 4.9 ×10⁹/L (2.0–7.5), platelets 268 ×10⁹/L (150–400) CRP 4 mg/L (<5) Na⁺ 138 mmol/L (135–145), K⁺ 4.3 mmol/L (3.5–5.3), creatinine 124 µmol/L (45–90), eGFR 37 mL/min/1.73 m² (>60) Corrected Ca²⁺ 2.34 mmol/L (2.20–2.60), capillary blood glucose 6.2 mmol/L (4.0–7.8), TSH 2.4 mU/L (0.4–4.0) Midstream specimen of urine (non-catheter) sent 2 days ago and reported today — microscopy: white cells 60 ×10⁶/L, red cells <10 ×10⁶/L, no epithelial cells seen; culture: Escherichia coli, pure growth >10⁸ colony-forming units/L, sensitive to nitrofurantoin, cefalexin, co-amoxiclav, ciprofloxacin and gentamicin, resistant to amoxicillin and trimethoprim; laboratory comment: pure growth of a single organism, susceptibilities are reported for guidance Chest radiograph the same day: no consolidation
- admit to hospital for intravenous antibiotics
- no antibiotic; investigate other causes of the delirium
- start cefalexin 250 mg PO 8-hrly for 7 days
- start nitrofurantoin 100 mg modified-release PO 12-hrly for 3 days
- start trimethoprim 200 mg PO 12-hrly for 3 days
Answer and marking
no antibiotic; investigate other causes of the delirium
Marks2
ExplanationBacteriuria is common in older people living in care homes and rises further with age and frailty; a positive culture on its own therefore says very little. It becomes a urinary tract infection only when it is accompanied by urinary symptoms — dysuria, new frequency or urgency, new incontinence, suprapubic or loin pain — or by systemic features of infection. This woman has none of them. She is afebrile, her white cell count is 7.8 ×10⁹/L and her C-reactive protein is 4 mg/L. What she has is asymptomatic bacteriuria, and NICE NG109 and NICE QS90 are explicit that antibacterials should not be prescribed for it in men or non-pregnant women, including older people. The white cells seen on microscopy do not change this: pyuria accompanies asymptomatic bacteriuria and is not itself an indication.
She does have delirium — a 4AT score of 5 with acute onset, inattention and drowsiness — and the obligation the culture must not be allowed to displace is to look for its cause. Two candidates are already on the page: codeine phosphate started 3 weeks ago after a vertebral fracture, and constipation with one bowel motion in 5 days and palpable faecal loading. Pain, dehydration, hypoxia, biochemical disturbance and any recent medicine change all belong in the same screen.
Why not the others? Cefalexin is sensitive on the report and the dose offered is already the reduced one for her renal function — her Cockcroft–Gault creatinine clearance is about 28 mL/min at 82 years, 58 kg and a creatinine of 124 µmol/L, and 250 mg 8-hrly is what that clearance permits — but there is no infection to treat, and the course would risk Clostridioides difficile infection and diarrhoea that would worsen the delirium. Nitrofurantoin fails on the same indication argument and is contraindicated below an eGFR of 45 mL/min/1.73 m². Trimethoprim fails twice: the isolate is reported resistant, and trimethoprim raises creatinine and potassium in impaired renal function. Admission for intravenous antibiotics treats a sepsis that the observations and inflammatory markers exclude, and moving a delirious patient out of familiar surroundings usually makes her worse (NICE NG109, 2018, current 2026; NICE QS90 statement 3; NICE CG103 delirium; UKHSA diagnosis of urinary tract infections quick reference tool).
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How to approach a data interpretation item
The repeatable method from the Data Interpretation section guide.
- Spot the abnormalityRead every result against its range. Note direction and, where given, the trend.
- Decide whether it is significantDoes it cross a threshold that changes management, or is it noise?
- Link it to a medicineWhich drug could have caused it, and which drug's dosing depends on it?
- Find the action thresholdMonitoring requirements or renal impairment sections state when to act.
- Continue, adjust, hold or stopChoose the action, and only the action, the threshold calls for.
Before you submit
- Have I found the result tied to a medicine, not just an abnormal one?
- Is it significant, or noise?
- Which drug does this threshold apply to?
- Is my action the one the threshold calls for, no more and no less?
- Would a second result confirm a trend before acting?
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