We are proud to be able to offer our expertise, capabilities and infrastructure as part of the solution on facilitating the national distribution of COVID-19 therapies, to supporting the distribution of more than 75 million vaccines to patients in over 30 countries through our expanded global footprint.
In July, for the fifth year in a row and for the tenth year of the past 12 years, Good Neighbor Pharmacy network was ranked highest among brick-and-mortar chain drug store pharmacies by JD Colin.
Earlier, I mentioned the distribution of tens of millions of doses of the COVID-19 vaccines to patients in more than 30 countries.
Now powered by 42,000 team members globally, we remain confident in our pharmaceutical-centric strategy and capabilities as a leader in pharmaceutical distribution services and differentiated manufacturer solutions.
Beginning with our fourth quarter results, we finished the quarter with adjusted diluted earnings per share of $2.39, an increase of 26.5%, which was driven by both a full quarter's worth of contribution from Alliance Healthcare and the strong performance in our Pharmaceutical Distribution Services segment.
Our consolidated revenue was $58.9 million, up approximately 20%, reflecting growth in Pharmaceutical Distribution and Other.
Excluding Alliance Healthcare, our consolidated revenue would have been up 9% from the prior year quarter.
Consolidated gross profit was $2 billion, up 51%, driven by increases in gross profit in both Pharmaceutical Distribution and other, which benefited from the inclusion of Alliance Healthcare.
This quarter's gross profit margin of 3.4% is 71 basis points higher than the prior year quarter as we had a full quarter of Alliance Healthcare in our consolidated results.
Consolidated operating expenses were $1.3 billion versus $795 million in the prior year period, primarily due to the addition of Alliance Healthcare as well as investments in our talent and initiatives to support the company's current and future growth.
This quarter's operating expense margin of 2.23% is 61 basis points higher than the prior year quarter, primarily reflecting the full quarter impact of Alliance Healthcare in our consolidated results.
Also as a reminder, in the fourth quarter of fiscal 2020, we had a bad debt reversal of $13 million that impacts the year-over-year comparison of operating expenses.
Our operating income was $694 million, up 31% compared to the prior year quarter.
Operating income margin was 1.18%, an increase of 10 basis points as a result of the contribution from Alliance Healthcare and the continued benefit from some of our higher-margin businesses.
Net interest expense was $55 million, up 57% due to debt related to Alliance Healthcare.
Our effective income tax rate was 20.3% compared to 21.7% in the prior year quarter.
Our diluted share count was 210.8 million shares, a 2.2% increase due to the impact of the issuance accumulated shares delivered to Walgreens as part of the Alliance Healthcare acquisition and dilution related to employee stock compensation.
Pharmaceutical Distribution Services segment revenue was $51.2 billion, up 8% in the quarter, driven by increased sales of specialty products, strong execution across our Pharmaceutical Distribution businesses and overall positive prescription utilization trends.
Pharmaceutical Distribution Services segment operating income increased by 11% to $472 million.
Operating income margin expanded by two basis points to 0.92% in the quarter.
In the quarter, Other revenue was $7.7 billion, up from $2 billion in the fourth quarter of fiscal 2020, driven by a full quarter's worth of contribution from Alliance Healthcare as well as growth in the global commercialization services and Animal Health businesses.
Other operating income was $223 million, up from $105 million in the fourth quarter of fiscal 2020 due to the inclusion of Alliance Healthcare.
Our consolidated revenue was $214 million, up 13%, driven by growth in Pharmaceutical Distribution and Other, which includes four months of contribution from Alliance Healthcare.
Excluding Alliance Healthcare, our consolidated revenue was up 9% from the prior year.
Consolidated operating income grew 20% for the year to $2.6 billion, driven by strong performance across our businesses and the four-month contribution of Alliance Healthcare.
Excluding Alliance Healthcare, our consolidated operating income increased by an exceptional 12% from the prior year, driven by growth in our higher-margin businesses, strong fundamentals across our business and the important work our team has done to support the COVID therapy distribution for hospitalized patients.
From a segment perspective, Pharmaceutical Distribution Services had operating income growth of 13% due to strong performance across our portfolio of businesses and customers.
In Other, operating income grew 54% year-over-year to $615 million.
Our adjusted effective tax rate for fiscal 2021 was 21.3% compared to 20.8% in the prior fiscal year, which has benefited from discrete tax items.
Our full year adjusted diluted earnings per share grew 17% and $9.26, primarily due to strong growth and execution across our business, including continued leadership and outperformance in specialty and the four-month contribution from Alliance Healthcare.
Adjusted free cash flow for the year was $2.1 billion, which was better than our expectations due primarily to the timing of certain customer payments in September, a benefit that will reverse in the December quarter due to the higher supplier payables.
If you normalize for the timing-related benefit, our adjusted free cash flow for the year would have been roughly $1.7 million.
We ended the year with a cash balance of $2.5 billion, excluding restricted cash of approximately $500 million.
On a segment level, we expect U.S. Healthcare Solutions revenue to be approximately $207 billion to $212 billion, representing growth of 2% to 5% year-over-year.
In International Healthcare Solutions, we expect revenue of approximately $26 billion to $27 billion.
On a segment level, we expect U.S. Healthcare Solutions operating income to be between $2.325 billion and $2.4 billion, representing growth of 3% to 6% on a year-over-year basis.
The only business that was included in Pharmaceutical Distribution services that is not going into U.S. Health Care Solutions is Profarma Distribution, which contributed less than 1% of revenues for Pharmaceutical Distribution Services in fiscal 2021 and roughly 1% of segment operating income.
The final earnings per share benefit from COVID therapy sales for full year fiscal 2021 was $0.30, $0.14 of which was in the first quarter.
If you estimate the first quarter of fiscal 2022 based on even lower October trends, the contribution from COVID therapy sales would be $0.03, which means the first quarter would have an $0.11 headwind for U.S. Healthcare Solutions segment.
While this reduces the segment's growth rate in the first fiscal quarter, we expect full year operating income growth of 3% to 6% in U.S. Health Care Solutions.
We expect International Healthcare Solutions have operating income between $685 million and $715 million.
Alliance Healthcare represents a little over 2/3 of operating income in the segment, with World Courier making up the majority of the remainder of segment operating income.
As you think about your first quarter models, we expect about 25% of the International segment's operating income to occur in the first quarter.
Successful completion of the divestiture is factored into our guidance and represents a 2% headwind to our International Healthcare Solutions segment's operating income.
We expect our tax rate to be approximately 21% to 22% for fiscal 2022, based on current tax rates in effect for fiscal 2022.
Without the tax rate benefit from Alliance Healthcare's operations, our range would have been 1% higher on both the top and bottom end of the range.
Finally, we expect that our share count will increase to approximately 212 million shares as a result of the full year impact of the two million shares delivered to Walgreens as part of the closing of the Alliance Healthcare acquisition and normal dilution from stock compensation expense.
As a reminder, as part of our commitment to maintain our strong investment grade credit rating, we are committed to paying down $2 billion in total debt over the next two years in lieu of share repurchases.
As a result of these expectations, reflecting the strength of our business, we are guiding for adjusted diluted earnings per share to be in the range of $10.50 to $10.80, reflecting year-over-year growth of 13% to 17%.
capex is expected to be in the range of $500 million as we continue to invest to further advance our business or to buy Alliance Healthcare's IT infrastructure and support additional growth opportunities.
For adjusted free cash flow, we expect adjusted free cash flow to be in the range of $2 billion to $2.5 billion, which includes the benefit of Alliance Healthcare in our results for the entire fiscal year.
I am proud of our 42,000 team members, who worked tirelessly to support our customers, partners and patients and drove our strong financial results.

Summary:
Beginning with our fourth quarter results, we finished the quarter with adjusted diluted earnings per share of $2.39, an increase of 26.5%, which was driven by both a full quarter's worth of contribution from Alliance Healthcare and the strong performance in our Pharmaceutical Distribution Services segment.