ANAEMIA: FERRITIN CAN DIAGNOSE IRON DEFICIENCY IN THE ELDERLY

Clinical Scenario: 75 y/o retired school mistress (in for a check-up) found to have a Hb of 10, with an MCV of 80, a negative history and physical, and no meds likely to suppress her marrow or cause a bleed.

Three-part Question: In an elderly symptomless woman with mild anaemia, would a serum ferritin help determine whether her bone marrow iron stores were depleted?

Search Terms: in Best Evidence, I searched on "ferritin" and got 6 hits (plus normal values), including a great single study and an overview.

The Study:

Independent..?	yes
Blind..?	yes
Standard applied regardless of test result..?	yes
Appropriate spectrum..?	can't tell

Target disorder and Gold Standard: Bone marrow, stained for iron.
Patients: Consecutive anaemic patients in several in-pt and out-pt settings. Transfused patients excluded.
Diagnostic test: Serum ferritin by radioimmunoassay.

The Evidence:

	Present		Absent
Test Result	Num.	Prop.	Num.	Prop.	LR
<15	474	0.59	20	0.01	51.85
15-34	175	0.22	79	0.04	4.85
35-64	82	0.10	171	0.11	1.05
65-94	30	0.04	168	0.09	0.39
=>95	48	0.06	1332	0.75	0.08

Comments:

1. For elderly patients with symptomless anaemia, go to the CAT on ANAEMIA IN THE ELDERLY to determine the yields from upper and lower g-i investigations.
2. Lots of labs are very slow in returning ferritin requests.

Expiry date: July 1998

References:

1. Guyatt GH, Oxman AD, Ali M et al: Laboratory diagnosis of iron-deficiency anemia: and overview. J Gen Intern Med 1992;7:45-53.
2. Patterson C, Guyatt GH, Singer J, Ali M, Turpie I: Iron deficiency in the elderly: the diagnostic process. Can Med Assoc J 1991;144:435-40.

Particular to my patient:

Pre-test probability: 67%

Test Result	Post-test probability
<15	99%
15-34	91%
35-64	68%
65-94	44%
=>95	14%

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