Final answer:
An elevated erythrocyte sedimentation rate (ESR) is an unexpected finding in a client who sustained a compound fracture and indicates a potential manifestation of osteomyelitis, a bone infection which requires reporting to the healthcare provider.
Step-by-step explanation:
The unexpected laboratory finding that suggests a manifestation of osteomyelitis in a client who sustained a compound fracture 3 weeks ago is B. Elevated erythrocyte sedimentation rate (ESR). Osteomyelitis is an infection of bone, and one of its signs is an increased inflammatory response. Elevated ESR, along with elevated C-reactive protein (CRP), indicates an acute inflammatory response, which is common in osteomyelitis. It is important for these abnormal levels to be reported to the healthcare provider as they may signal the need for further investigation or treatment modifications.
A decreased white blood cell count would not typically be associated with infection, as infection often causes an increase in white blood cells. An increased alkaline phosphatase level can be associated with bone healing or growth, but it is not specific to osteomyelitis.